Popular Science Monthly/Volume 19/May 1881/Popular Miscellany


Health and Material Prosperity.—The report of the Board of Health of New Haven contains, in a letter from Professor Brewer, President of the Board, to the Common Council of the city, a convincing statement of the closeness of the relation between a good sanitary condition and the material prosperity and wealth of a city or community. An individual, to prosper by his labor, must be reasonably well; the same is equally true of a community or state. In the intense competition of modern times, no sickly community can be prosperous. It may be intelligent, and moral, and industrious, but it must be poor. Hence it is a duty, imposed not only by the claim of the individual on the community, but also by the vital interest of the community itself, to protect every person in it against those diseases and dangers whose power for evil has grown along with our civilization. The wonderfully rapid accumulation of wealth, far surpassing anything ever witnessed in the past, which is one of the characteristics of modern times, is not due to improvements in machinery, to applications of science, to the spread of education, the decrease of wars, or the more extended production of precious metals, though all these have contributed their part, so much as to the better average health of civilized countries and the longer average term of life which is now secured to workingmen. Even now, a single pestilence like those with which Savannah and Memphis have recently been afflicted, may set the most prosperous city back many years. New Haven has had but one visitation of yellow fever, but it took the city eight or ten years to recover from the visible effects of it, and a permanent loss of "what might have been" was suffered at a critical period in the commercial development of the city, the value of which can never be ascertained or guessed. The sanitary work, which is of such importance in this aspect of civic life, is often overlooked, because of its unobtrusive character; and it is never more efficient than when it is least obtrusive. In the ordinary pursuits of business, the clang of machinery, brilliant scientific applications, the bustle, etc., "are more conspicuously in the eyes of the public than the quiet, persistent, unromantic, but heroic fight with unseen but unwholesome influences which lurk in the air of our towns. These influences, mostly growing out of our modes of life, are ever present in all our cities, ever growing unless checked, always producing disease, and from time to time especially inviting pestilence." Few cities can afford to allow a pestilence to invade them. "A single epidemic, but one fourth as bad as that of Memphis last year, would cost this city," says Professor Brewer, speaking of New Haven, "more, and leave us with higher taxes, than the most expensive system of sewers and of garbage collection that was ever dreamed of here." Moreover, a pestilence is only an intensified manifestation of disease, and most of its disastrous effects may be produced by prolonged but general ill health; and it is perfectly safe to say that no Northern city can be really prosperous and really sickly at the same time.

The Mound-Builders.—The report of retiring President Pratt, of the Academy of Sciences of Davenport, Iowa, gives especial attention to the researches respecting the mound-builders, in which this association is much interested. One of the members of the society, the Rev. Mr. Gass, explored seventy-five mounds during 1880, about fifteen of which afforded relics to be deposited in the museum. According to the evidence of the mounds in the vicinity of Davenport, copper was a rare and highly valued article among the people who built them, so rare as to indicate that they did not work the copper-mines of Lake Superior or any others, and were not in communication with any people who did. The amount of drift copper still found in the region indicates that a sufficient supply for all that the mound-builders seem to have had could be accounted for from that source. The copper was all hammered; no evidence exists of any of it ever having been smelted or cast. The so-called copper axes do not seem ever to have been used as tools, and are supposed to have been kept as badges of wealth and distinction. The mound-builders smoked tobacco, but, as is inferred from the form of the pipes, ceremonially rather than for enjoyment. Among the great variety of animal forms represented on the pipes, two distinctly resemble the elephant, mammoth, or mastodon. Mr. Pratt declares that the Davenport Academy has evidence—the only evidence discovered so far—that the mound-builders had a written language. It exists in the shape of two inscribed tablets found in the mounds and deposited in the museum of the society, which have attracted considerable attention in this country and Europe, and to which, provided their genuineness can be maintained, much importance is naturally attached by archæologists. They were kept at the Smithsonian Institution for two months, and were carefully examined there by members of the National Academy of Sciences as well as by other persons; heliotype plates were taken of them, and they were exhibited at the meeting of the American Association at Boston last August. Mr. Pratt believes that the evidence of their genuineness is sufficient. The society's collection of mound-relics is regarded as one of the best in the world.

The Saliva and the Gastric Juice.—Recent researches reported by M. Defresne throw new light on the relations of ptyaline, diastase, and the gastric juice. It has been debated whether the saliva is destroyed in the gastric juice or continues in the stomach its action on starch. M. Defresne's experiments prove that the saliva is paralyzed in pure gastric juice, but that with a mixed gastric juice containing only organic acids, saccharification proceeds as well as in the mouth. Ptyaline, then, differs from diastase in that it is only paralyzed for an instant in pure gastric juice, but recovers its action in the mixed gastric juice and in the duodenum, and is capable of continuing the process of saccharification; while diastase is irrecoverably destroyed in hydrochloric solutions or in pure gastric juice, and is profoundly altered after passing into the mixed gastric juice, so that if it still dissolves starch it no longer saccharifies it. Ptyaline is recommended as an excellent reagent for demonstrating the difference between mixed gastric juice, which owes its acidity to organic acids, and pure gastric juice, the strength of which is derived from hydrochloric acid.

Cutting and Slave-making Ants.—The Rev. Henry C. McCook has contributed to the Academy of Natural Sciences, of Philadelphia, papers on a Northern cutting ant, and on the American slave-making ant, both of which are of much interest. The cutting ant was observed at Island Heights on Tom's River, New Jersey. Entrance to the nest was afforded by a narrow tubular gallery about two inches long, which led to a spherical chamber about an inch and a half in diameter. This chamber, or vestibule, communicated with another chamber, also generally spherical, but of more irregular outline, three and a half inches in diameter, within which were several masses of leaf-paper similar to that made by the Texas leaf-cutting ant, but exceedingly fragile and without the cellular arrangement of the Texas paper. In pleasant weather the insects worked in two columns, one going each way—to the pine-trees and returning to the nest—and moving very deliberately. Those in the column returning homeward were carrying little pieces of the pine-needle or leaf, cut from seedling plants. They bore the load on the head, with one end held firmly by the mandibles, and the effect at a little distance was "to give them a shoulder-arms appearance." In cutting the leaf, the ant climbed out to a position near the end and applied her mandibles, moving around as she cut, till the piece was severed and fell. The architecture of the caves was a miniature copy of those of the Texas cutting ant. All the colonies were comparatively small, and without visible connection with each other. The slave-making ants (Polyergus lucidus) were studied near Altoona, Pennsylvania. They occupied a chambered nest which was furnished with four gates, and extended to the depth of at least twenty-two inches underground; but the chambers were without orderly arrangement, apparently on account of the gravelly nature of the soil in which they were built. Mingled in large numbers with the lucidus ants were working insects, of the species Formica Schauffussi. Two days after the nest was disturbed, the working ants were observed cleaning out the galleries, with the apparent intention of closing the openings. Others were engaged in a migration, taking up the mistress ants by interlocking mandibles with them, and carrying them off up the perpendicular face of the cutting for eighteen or twenty inches, and then for the distance of six feet over the ground and through the grass. "More than once a slight opposition was made to this treatment. The slaves, or at least certain individuals of them, . . . seemed at times to have a prejudice against the presence of lucidus ants above-ground, and would unceremoniously seize them and carry them below. I have seen a master, or more properly 'mistress,' thus served several times, each time returning in a dogged sort of resistance to the will of her servitor. These inert mistresses, too, apparently know something of the bitterness of bondage to a capricious domestic help!" In the course of the migration, one queen was seen to resist carriage so vigorously that she was finally dropped, and, refusing to give the slave a hold on the mandibles, was seized by the wing and dragged off. "The lucidus ants seemed to have no volition in or direction of this movement. I released a number from their porters during various stages of the transit, and they always wandered about with a confused, aimless, and irritated manner until again seized and borne off by slaves." Some of the ants were colonized in Philadelphia, and observed more closely. The masters were never seen to work. "The colony was changed several times in order to incite to new work in mining galleries and rooms; clusters of lucidus were placed by themselves; they always remained idle. The slaves wrought with the greatest industry and energy as long as there was any need: the masters would crowd into the galleries, and move about in an aimless way, but I never could trace any attempt either at directing or aiding in the work. So, also, I never saw one attempt to eat. . . . Yet they are in good condition, and evidently well fed. They are doubtless fed by the workers, who must disgorge the food." But Dr. McCook could not see this going on. The lucidus ants and the workers both seemed fond of the light, even of the artificial warmth and light of the gas-light globe, where they would "congregate in the comfortable glow." The association of the two species in their singular relations has resulted in developing the warlike faculties of lucidus at the expense of its disposition to labor; but has not operated to degenerate the soldierly courage and faculty of Formica Schauffussi, the working ant, for the individuals of this species will spring to repel a hostile attack as freely and fiercely as their masters, and will do it independently, too; and they are quite as able as ready to wage sucessful warfare. The lucidus ant appears to be spread over the whole continent, except perhaps in the far south.

Improved Electric Motor.—A new form of dynamo-machine has recently been devised by Mr. C. F. Heinrich, which the "Telegraphic Journal" pronounces an important advance upon previous constructions. The main improvement is in the form of the armature, which the inventor has been led to adopt by a careful study of the Gramme ring and the way in which currents are induced in it. He finds that the inner side of the ring (that farthest from the field magnet) produces on the coil a current opposed to the one induced on the part of the coil immediately in front of the poles of this magnet, and to this extent weakens the current and causes heat in the coil. When the field magnet is powerful and the ring thin, this effect is reduced, but the inductive action of the farther side of the ring is not wholly eliminated. He therefore makes the ring channeled, or of horseshoe cross-section, the coils of wire being wound on the outside only. This removes the metal from the inner portion, and at the same time allows such a free circulation of air around the wires of the coil where they cross the base of the horseshoe that heating is effectually prevented. The ring is mounted and revolved between the poles of the field magnet in the same way as on the Gramme machine.

Geological Features of Behring Strait.—Some curious geological features are noticed in Mr. W. H. Dall's report of his last summer's work in the coast and geodetic survey of Alaska and the vicinity of Behring Strait. The country is not wholly without attractions, for when, on the 20th of August, the surveying-vessel, the Yukon, anchored behind Cape Lisburne, on the American shore of the Arctic Ocean, nearly two hundred miles north of Behring Strait, the air was balmy, the sun was warm and bright, no snow or ice was visible, and the banks were covered with flowers, among which daisies, monk's hood, and forget-me-nots were conspicuous. At Point Belcher, too, the vegetation was quite dense. Beds of good coal, belonging to the true Carboniferous period, are found at Cape Lisburne, from which the revenue cutter Corwin was satisfactorily coaled several times. Large lumps of coal lay on the beach at Point Belcher, which had been pushed up by the ice from the bottom of the sea. The peculiar geological feature of this region is a great formation of ice which seems to have the characteristics of a regularly stratified rock. At Point Belcher, pure ice is met at two feet below the surface, and is of unknown depth. At Elephant Point, Kotzebue Sound, the clay banks gradually rising along the beach to the eastward show successively two perpendicular faces of ice, "solid and free from mixture of soil, except on the outside," one above the other. The ice-face nearest the beach is covered with a coating of soil which bears a luxuriant vegetation. The whole formation, including the talus in front of the ice, may be about thirty feet high. Above this is a second talus, on a larger scale, ascending to the foot of another ice-face, which is also covered with herbage-bearing soil. The brow of the second bluff is about eighty feet above the sea; from it the land rises gradually to a rounded ridge three or four hundred feet high. At the height of two hundred and fifty feet a frozen stratum was found containing lumps of clear ice, that indicated the existence of solid ice, at no great depth below. Hence it is inferred that the whole ridge, two miles wide and two hundred and fifty feet high, is chiefly composed of solid ice overlaid with clay and vegetable mold. The ice generally has a semi-stratified appearance, is only superficially soiled, is granular in structure for the outer inch or two, and internally solid and transparent or slightly tinged with yellow; but is never greenish or bluish, like glacier-ice. Small pinnacles of ice run up into the clay in places, while in other places the ice itself is penetrated with deep holes in which clay and vegetable matter have been deposited. Holes were seen in the clay-molds of spurs of ice that had been melted away, and cylinders of muck and clay were found on the ice-face, that had once filled holes from around which the ice had melted. A strong, peculiar smell was often noticed, apparently emanating from dark, pasty spots in the clay. It was supposed to proceed from the decomposition of the remains of soft parts of mammoths and other animals. Birches and alders seven or eight feet high, luxuriant herbage, and plants bearing delicious berries, grew with their roots less than a foot from perpetual solid ice. Observations on the water in the strait showed that it is warmest toward the American side, and becomes gradually cooler toward the Asiatic side; that the temperatures are nearly uniform from top to bottom, precluding the idea of the existence of a sub-surface current from the Arctic Ocean which carries cold water to the south; and that the northerly current through the strait and along the Arctic Ocean is probably chiefly dependent on the tide for its force and direction, and upon the warming of shallow waters for its high temperature.

Minnesota Academy of Sciences.—The Minnesota Academy of Sciences was organized seven years ago, and is now free from debt, and able to report its library and cabinet in creditable condition. Although it has had to encounter a lack of sympathy from part of the community, on account of an apprehension that its tendency might be toward infidelity, the retiring President, Dr. F. L. Hatch, declared at the annual meeting last January, that in none of the papers read and published under the sanction of the Academy had any dogma of any one's faith been touched, or a derogatory reflection been cast upon the Christian's sacred record. Professor N. H. Winchell, the incoming President, made an address at the annual meeting, maintaining the right and duty of the State to establish and support institutions for the higher education. He endeavored to show that the denominational colleges and universities had been backward in responding to the demand for the provision of more liberal courses of scientific instruction; and that no general movement was made by them in this direction till a system of scientific schools had been established by private enterprise and State aid, independently of them, and in the face of their indifference to the scheme.

Units of Electrical Measurement.—The International Congress of Electricians, to be held in Paris during the summer, will doubtless be called upon to consider the subject of a uniform standard for electrical measurements. The system of standards at present most used was adopted by the British Association after eight years of study and experiment by a committee. In it all the units of measurement are referred to three fundamental units, the centimetre, the gramme, and the secund, whence it is called the centimetre-gramme-secund system of units (expressed by the symbol C. G. S.). The units practically employed—multiples or sub-multiples of the fundamental units—are the ohm, or unit of resistance (symbol R.), the volt, or unit of electro-motive force (symbol E.), and the weber, or unit of intensity (symbol I.). Their relation to each other is expressed by the equation, I ER' whence, the value of two of the elements being known, that of the other can be determined. The unit of resistance, or ohm, is determined by a long and complicated formula, so that it is easier to get it at once by comparison with the material standard which is kept at London. Graduated resistance-boxes containing electric coils carefully adjusted to the resistance-force they are intended to represent, are sold by the instrument-makers. Some idea of what the ohm is may be given by saying that a wire of pure copper a metre (or 3913 inches) long and a milimeter in diameter (or about 125 of an inch) represents a resistance of one fiftieth of an ohm; consequently, fifty metres, or one hundred and fifty and a half feet of such wire, will represent an ohm. Common copper wire offers a stronger resistance, so that only thirty or forty metres of it are required to represent an ohm. The volt, or unit of electro-motive force, is not represented by any actual exact standard, but several constant piles exist, the force of which has been exactly measured, which may be referred to. A Daniell battery, having its copper immersed in a saturated solution of sulphate of copper, and its zinc in a saturated solution of sulphate of zinc, has a force of 1·079 volt. The electro-motive force may be measured in practice by using galvanometers which are graduated in volts, the exactness of which is proportioned to the amount of the resistance they offer. One weber represents the intensity of a current having a force of a volt and passing over a circuit which offers an ohm of resistance. The intensities of currents in ordinary industrial use are represented by fractional units of the weber, the milliweber, or thousandth of a weber, for telegraphic, domestic, and medical currents, the microweber, or millionth of a weber, for telephonic currents. Telegraphic currents vary in intensity from five to twenty milliwebers; the currents of the Gramme machines that feed the Serrin regulators, of from twenty to thirty webers. Some machines used in electrotyping afford still more intense currents, often exceeding eighty webers, although their electro-motive force is very feeble. In France they sometimes measure by the kilometre of resistance, meaning by that the resistance which is offered by a telegraphic wire four millimetres or about one sixth of an inch in diameter, and a thousand metres or five furlongs long, which is equivalent to about ten ohms. The unit of Siemens (U. S.), employed in Germany, represents the elastic resistance of a column of mercury having the length of a metre and a section of a square millimetre, and is equivalent to 0·9536 of an ohm. Several units of intensity founded on the chemical action of electric currents are in use—such, for example, as may be founded on the quantity of gases disengaged in a minute by a voltameter placed in a circuit, or the amount of copper that may be deposited in an hour in an electrolytic bath which is traversed by the current to be measured. Standard apparatuses have also been made, so graduated as to furnish on a simple reading the intensities in webers and microwebers.

German Anthropology.—The German anthropologists are making a study of the relative distribution of blondes and brunettes in aid of their investigation of the origin and ethnological composition of the German people. The reports on this subject, presented by Professor Virchow to the recent German Anthropological Congress, seemed to indicate the existence of centers of light-colored populations in Schleswig-Holstein, the country of the lower Elbe, Hanover, and Pomerania, and of dark-colored stocks in Bavaria, along the Rhine, in western Belgium, and in Switzerland. No superiority over the other is ascribed to either complexion, but the difference is one of original stocks. The blondes appear to have come down from the northeast of Europe and pressed the native dark race upon the mountain-spurs and the upper valleys. Herr Eckert reported to the Congress concerning the progress he had made in determining the differences in the skulls of the sexes. The feminine skull appears to be marked by a smaller volume, greater delicacy in the contours of the orbits and the structure of the jaws, the absence or inferior importance of the frontal sinus, a more gradual passage from the forehead to the root of the nose, and a flattening of the parietal bone. A discussion took place respecting some Arabic silver ornaments and filigrees of the tenth and eleventh centuries which have been found in Northern and Eastern Europe. Virchow has concluded, from the occurrence of these articles, that an extensive trade existed in the ninth and tenth centuries between the regions of the Volga, the Baltic ports, and the northern countries, and the coasts of the Black Sea and the East. These Arabic ornaments are very abundant in the province of Posen, in some parts of Russia, and in Gothland, and Arabic coins are found in Norway and Iceland. A paper was presented by Professor Ranke, based on the statistics of recruits for the year, which appeared to show that a relation exists between the character of the country and the size of the men who inhabit it. The higher mountain regions appear generally to produce the larger men. M. Kollmann, of Switzerland, read a paper showing that prognathism, which is believed to be an exclusive mark of inferior races, is of frequent occurrence among civilized people. The prognathous jaws which have hitherto been found in Europe have been considered as abnormal cases, or as examples of alveolar prognathism; but it is impossible exactly to separate alveolar from real prognathism. Some skulls from the heart of Germany, by whatever rules or lines they are measured, show a greater degree of prognathism than those of the negroes of Australia; and the conclusion can not be avoided that this feature is shared to a considerable extent by civilized people. An interesting communication was made concerning the skull of Emmanuel Kant, whose remains had been exhumed in order to place them in the tomb built for them by the city of Königsberg. Two skeletons were found together, but the remains of Kant were identified by comparing the skull with the cast which was preserved in the archives of Königsberg, with which it was found to correspond exactly. The bones of the nose were turned toward the right, and the superciliary arch had a greater development on the same side. The greatest cranial length was 182 millimetres, the height 132 millimetres, and the breadth 161 millimetres, while the mean breadth of Prussian skulls is only 144·6 millimetres. The forehead had none of the majesty attributed to a thinker; it was not broad, and was a little retreating. The temples had a fullness that compensated for this lack, and the left temple showed a protuberance in the region of the third frontal circumvolution, the region in which the faculty of controlling articulate speech is supposed to reside. The only extraordinary feature of the face was the height of the orbits.

Life and Nature in the Campos.—Dr. D. Christison's narrative of his journey to central Uruguay, given before the Royal Geographical Society last fall, is full of curious illustrations of the primitive character of the life in a country which, although it has great capacities for development, is as yet hardly known abroad. The region to which the description applies is the estancia of San Jorge, on the south bank of the Rio Negro, almost in the center of the republic, which embraces an area of three hundred and sixty-four square miles. The journey from Montevideo was made in a diligencia, an open omnibus in three compartments, holding twelve passengers, and drawn by six half-broken or unbroken horses, which are driven in a manner peculiar to the Campos. In order to prevent accidents from unperceived faults in the roads, a cuartiador rides about twenty yards ahead of the team and conducts it by means of a rope which at one end is fastened to the wagon-pole and loosely connected with the bridles of the leaders, and at the other end is attached to the saddle of his own horse. The stages are short, but the stops are very long, for the horses have to be driven in from the plain, and much talking has to be done before those which are needed are lassoed and harnessed to the wagon. "Sometimes an animal is selected, which has never been harnessed or handled before, and it is only after a long struggle, requiring the utmost skill and strength of the mayoral and his assistants, that it is subdued, great roughness being used in lassoing and throwing it, while it is approached and handled gently in harnessing." The road, like all the main routes in Uruguay, is called the camino real, or royal road, but the roads are all mere tracks over the Campos, chosen so as to avoid the steepest hills and seek the easiest places to ford the rivers. As a rule, the country can be crossed by ordinary stage-coaches on the natural turf in either direction. The landscape is tame and monotonous, disposed for the most part in low, gently sloping downs or ridges, rising from sixty to two hundred feet above the valleys, "covered with grass and generally unbroken by tree, bush, or rock." The ridges are not furrowed by ravines, and show no traces of erosion. Signs of human habitation are rare. In a few instances the view was relieved by two or three ombie-trees (Phytolacca dioica), "large, handsome, shady trees, with soft, pith-like stems." Near Florida were observed groups of stones, like cairns, "consisting of squarish blocks arranged in an artificial-looking manner," a similar formation to which, fifty miles farther west, called Serra, constitutes a true though miniature mountain-range, and has been compared by Dr. Burmeister to the "Teufelsmauern" and "Felsenmeere" of Germany. The district of San Jorge, judging from the rocks of the dividing ridges, rests on a formation of volcanic origin, and is remarkably well watered by the Rio Negro and its tributaries, the Carpinteria and Chileno, with numerous streams flowing through it. The mass of the country is covered with grass but destitute of timber, while the rivers are fringed with montes, dense belts of trees and shrubs. The grass is coarse and bunchy, endures the droughts of ordinary summers, and is profusely adorned with compositæ, yellow and purple oxalis, white, red, and scarlet verbenas, many liliaceous plants, and a fine œnothera. The only native tree on the Campos is a thorny tala (Celtis tala). The montes are of comparatively insignificant area, and are composed chiefly of willows, coronillos, laurels, the fruit-bearing guayavo, prickly climbers, and brush-wood, comprising more than twenty species in all. The larger animals—the jaguar, puma, great ant-bear, and large deer—have nearly disappeared, but the smaller animals and the rodents are well represented. Birds are numerous and extraordinarily tame. Eagles would let the traveler throw clods at them and almost touch them, and the rhea ostrich would allow a man on foot to approach to within seventy yards before walking or trotting off. The most important insect is the leaf-cutting ant, which has been often described. It parcels out the Campos among its communities, the nests of which are generally about a hundred yards from each other, with five or six paths radiating from each till they approach the domains of their neighbors. Along these paths double streams of workers are constantly passing to and from the country, each ant of the returning stream holding aloft a piece of grass, a leaf, or a flower. Gardens must be protected against them by destroying the nests with boiling water or poisonous solutions—a difficult task, which has to be carefully done. Another insect plague is the bicho moro, a blistering beetle, which attacks the potato-fields and eats regularly forward with almost incredible rapidity.—The return-journey to Montevideo was made in a bullock-wagon, a solidly built vehicle with an arched roof of zinc, perched on high, broad wheels made of pieces of wood so skillfully wedged together that every shock made them firmer, and drawn by means of a shaft which is of one piece with the body. The three or four yoke of powerful oxen, which form the team, are driven by a picador, who rides alongside, and the whole train, of which a single one of the wagons is only a member, is under the command of a mounted carretero, or patron. The rate of traveling is estimated at from twenty to twenty-four miles a day, but is largely dependent on the weather.

Physiology of Arsenical Poisoning.—MM. H. Caillet de Poncy and C. Livron, of the Medical School at Marseilles, have found that, when poisoning by arsenic takes place, the phosphorus which exists as phosphoric acid in the brain is replaced by arsenic. The substitution takes place in the lecithine, a very complex nitrogenized compound, which thus becomes transformed into an insoluble albuminoid substance. In acute poisoning there is no time for the arseniated lecithine to be subjected to physiological reactions and be eliminated, and the animal dies under the local influence of the poison without sensible variation of the normal phosphorus of the nervous matter. In slow and chronic poisoning the replacement takes place slowly; arseniated lecithine is formed, and acts as ordinary lecithine, passing gradually into the insoluble albuminoid state, while the phosphorus is steadily diminished, giving place to the arsenic.

The Otto of Roses.—The otto of roses consists of an odoriferous liquid containing oxygen combined with a solid hydrocarbon called stearoptene, which is destitute of perfume. The quality of the oil is determined by the relative proportion of these substances, and that is dependent chiefly on conditions of climate. The Bulgarian oils contain about eighteen per cent., the oils distilled in France and England as much as thirty-five and even sixty-eight per cent. of stearoptene. The difference in the proportions is also shown in the higher temperature required to melt the oil which contains a greater relative amount of stearoptene. The Bulgarian oil melts at from 61° to 64°, French and English oils from 70° to 8912°. Even in Bulgarian oil a notable difference is observed between that produced on the hills and that from the lowlands. The most important source of otto of roses is a small district in Bulgaria or East Roumelia, stretching along the southern slopes of the central Balkans, and approximately included between the twenty-fifth and twenty-sixth degrees of east longitude and the forty-second and forty-third degrees of north latitude. A suitable soil for the growth of roses is furnished, with need for but little manuring, by the decomposition of the syenite, which is the characteristic rock of the region. The average summer temperatures of the district are 86° at noon, and 68 in the evening. The rose-bushes do best on sandy slopes having a good exposure to the sun. The flowers of bushes which grow on inclined ground are much richer in oil, and that of a stronger quality, than those raised on level land, and are therefore more esteemed and dearer. The flowers when fully expanded are gathered before sunrise, often with the calyx attached, and should be treated the same day. In Bulgaria, roses which have matured slowly in moderately cold weather furnish the richest yields; in England, the contrary appears to be the case. The flowers are distilled for an hour and a half, with double their volume of water, in a copper still from which a pipe passes through a tub that is kept constantly cool by inflowing spring-water. After the distillate has been allowed to stand for a day or two at a temperature exceeding 59°, the oil is skimmed off from it. The residual liquors are used instead of spring-water for subsequent distillations. The rose-water which comes over last is extremely fragrant, and is much prized for medical and culinary purposes. Pure otto, carefully distilled, is at first colorless, but speedily becomes yellowish; has a specific gravity of about 0·87, boils at 444°, and solidifies at from 51·8° to 60·8°, or at higher temperatures in the case of inferior oils, and is soluble in absolute alcohol. It is tested by its odor, which can be judged only after long experience; its congealing-point (a good oil should congeal in five minutes at a temperature of 54·5°), and by the crystallization of the stearoptene with light, feathery, shining plates filling the whole liquid. It is sometimes adulterated with spermaceti, which may be detected by its readiness to solidify, and by other essential oils, the effect of which is sometimes to lower the congealing-point. Rose-water and otto of roses are also produced in India; in Persia, where the trade, formerly important, has nearly disappeared; in the Mediterranean countries of Africa, and in France. The otto of the Provence rose has a characteristic perfume, which arises, it is believed, from the pollen of orange-flowers, which is brought by bees to the petals of the roses.

Effects of Petting on Animals.—Mr. A. D. Bartlett, of the Zoölogical Gardens, London, has remarked that while adult carnivorous animals—lions, tigers, leopards, etc.—can seldom be tamed and then only at the cost of danger, the young become very tame and fond of those who feed and caress them; on the other hand, housed vegetable-feeding animals—stags, antelopes, oxen, sheep, and goats—if reared by hand from birth, become when adult the most dangerous animals to be met with; while, if caught after they have grown up, they are timid and fly from man. His experience with all animals of the latter class has been the same as with the lamb, whose case he describes, that was brought up as "one of the family." As it grew larger and stronger, it became self-conscious and independent, having "no fear and less gratitude," and grew so saucy that it had to be consigned to a large field, where it became a terror to passers—for, "with hop, skip, and jump, he was behind any one in an instant; with one good spring, the unfortunate traveler was on his hands and knees if not on his face"—and was finally sentenced to the butcher. Such of these animals as have been bred in captivity (not petted and handled) and reared by the parent, become exceedingly wild if an attempt is made to catch them, pack them up, or move them from one place to another. The reason for these curious manifestations appears to be that the tamed animals, having lost their fear of man and become familiar with him, when the time comes for them to manifest their belligerent propensities, have no respect of persons, and are ready to attack their former friend as they would any other real or imaginary antagonist; but, when anything new is attempted with them, it is as novel as it would be in their natural state, and awakens all their natural wildness.

Fungi as Insecticides.—The possibility of putting a limit to the depredations of noxious insects by cultivating the fungi which are destructive to them has been several times suggested. Professor Le Conte recommended the study of the epidemic diseases of insects, particularly of the fungoid diseases, with this view, in 1874. Charles II. Peck, State Botanist of New York, advanced a similar idea with reference to the fungi which infest plants, in 1876, and in 1878 described a large destruction of seventeen year-locusts and of the larvæ of insects feeding upon the alder by fungi. Dr. H. A. Hagen, of Harvard University, in 1879, thinking he had established the identity of the fungus which destroys the house-fly with the yeast-fungus, recommended the use of the latter against noxious insects in general. Professor A. N. Prentiss, of the Botanical Laboratory, instituted a series of experiments during the spring of 1880 with the plants in the laboratory, upon the effects of the yeast-fungus upon the aphides and other insects preying upon them. The record of his experiments is given in the form of a journal in contributions to "The American Naturalist." The result of nine experiments as a whole, as also of many others not recorded, indicates that yeast can not be regarded as a reliable remedy against such insects as commonly affect plants cultivated in greenhouses and dwellings. The attempt to use it is liable to the further objection, that it will be very likely to injure many kinds of plants quite as badly as it will the insects. The experiments of Mr. Trelease, of Selma, Alabama, with the yeast upon the cotton-worm, led him to a similar conclusion with reference to its application to that insect. On the other hand, according to Dr. Hagen, Mr. J. H. Burns, of Shelter Island, New York, has had some success with yeast against the Colorado potato beetle, and it has been used upon the aphides in a greenhouse in Germany with great success. Professor Prentiss does not consider the question at issue decided by his experiments, for the yeast-fungus may be operative on other insects and under other conditions than those with which he performed his experiments, and there may be other forms of fungus which, applied with discrimination, would be effective.

Examination of Germs in the Air.—Dr. Ferdinand Cohn and Dr. Miflet, of Breslau, have been investigating experimentally as to the possibility of detecting the organisms which are regarded as the germs of infection and fermentation in the air in which they are supposed to float. Their experiments were carried on from the middle of March to the end of July, 1878, in the air of laboratories, operating-rooms, and the sick-rooms of hospitals; in the free air of the botanical gardens, and the air gathered at the surface of the soil of the garden; and in the sewer-air of a court. They found—1. That numerous germs exist in the air in a suitable condition to undergo development; 2. That these germs could be collected by the methods they employed, could be made to develop and multiply, and could be systematically distinguished and described; 3. That the presence of some of the germs which are commonly developed in fermenting substances was not detected in the air; 4. That the presence of germs of particular kinds was detected in air taken from the surface of the soil; 5. That the air of the sick-chamber of a typhus-hospital appeared to be singularly free from germs capable of development, a result which was attributed to effective ventilation and disinfection; 6. That the air rising from the sewer was rich in living germs; 7. That the number of observations and experiments in this their first systematic investigation is not yet sufficient to enable them to determine whether the difference in the number of germs collected from the air in different places may be taken as indicating a difference in the healthiness of the several localities—so far, they seem to give a negative result.

Forestry in India.—An address by Sir William Temple, before the Society of Arts, on "Forest Conservancy in India," calls attention to the vast destruction of forests which that country has suffered in common with other populous lands. Traditions show that the country was once covered with sylvan and other vegetation, but this dress has been removed, as the demands of man upon the surface have increased, and the most important forest-growths are now found on the mountain-ranges. The trees of India may be divided into two classes; those of the Himalayas, and those of the other mountain-ranges and the plains. The trees of both classes are magnificent specimens of growth. The Himalayan trees are allied with those of Europe and other temperate regions, and embrace, among the Coniferæ, the cedar, the Pinus longifolia, most valuable timber-trees; the cypress, the fir, the yew, and the juniper, the latter the only valuable tree that grows near Quettah. Of the other orders are the ilex, oak, and walnut, of Simla, the plane-tree of Cashmere, the maple, magnolia, laurel—here a great tree—the rhododendron, and the tree-fern, most graceful of plants. The other mountains produce the teak, the iron-hearted sal, the anjun, with its white, bright, and smooth trunk like a great marble pillar; the saj, which often grows close by the anjun, and, having a black and rough trunk, offers an effective contrast with it; the black-barked bije sal; and the white-barked, weird-looking frankincense-tree. The plains furnish the babul, or acacia, the one tree which is universal in India; the mango, the figs, among which are the banyan; and the India-rubber tree, bamboos, and palms in their varieties. The demands of the population for wood are immense, with thirty-seven million houses in British India, and one fifth as many in the native states, to be supplied, and all the implements of a people with whom iron is in comparatively little use. On account of the scarcity of wood, the people are obliged to burn manure for fuel, and thus to rob the soil of what should be returned to it, adding another to the agencies which are steadily impoverishing it. The absence of woods can not affect the total rainfall of the country, for the vapors that rise from the sea must be condensed somewhere, but it seriously affects its disposition. The clouds pass over the hot, dry plains, and precipitate their moisture upon the mountains, where they cause swift torrents to rush down into the lower country and create destruction there. The capacity of the soil to retain moisture is destroyed, and the water which would be stored in the natural forest through the dry season is lost in a sudden drought. A Forest Department has been created by the Government within the last twenty years, and gives special attention to the preservation of the remaining forests, of which the whole extent is about seventy thousand square miles. These forests are divided into the "reserves," or forests which are carefully guarded, embracing about twenty-five thousand acres, and the "protected" forests, which are imperfectly guarded and preserved. The forests of both classes have been decided to be the property of the Government. The reserves are placed directly under the care of the Forest Department. The protected forests are managed by the ordinary civil officers, under the supervision of the Forest Department. The management is directed to the regulation of the cutting of timber, to the control of the practice called "rab," or of cutting the new shoots and twigs of trees to be burned for manure, to the prevention of jungle-fires, and to the regulation of pasturage by establishing blocks, or areas of forest range, to which grazing may be confined, while other blocks are held in reserve to be entered upon after the grass of the former blocks has been consumed. The restrictions are imposed only in those forests which have belonged from time immemorial to the Government, as well under native dynasties as under British rule; and, where subordinate rights exist, they are recognized and defined. Areas of jungle, of equal—probably of more than equal—extent with the forests, and ample for the general local use of the natives, have been everywhere marked off as belonging to the people, and are accessible to them without restriction. The "reserved" and "protected" forests furnish first and second class timber and excellent fuel. The management of the Forest Department has so far been attended with a considerable profit to the revenue of the state.

A New Disinfectant.—When warm air is forced through a hot mixture of turpentine and water, a disinfecting substance known in commerce as sanitas is produced. It is an aqueous solution, characterized by the presence of peroxide of hydrogen and certain camphoraceous substances. With it is found another substance, called sanitas-oil, also containing peroxide of hydrogen, which possesses a high power of oxidation. According to the account given of it by Mr. C. T. Kingzett, the oil promises to become very valuable for sanitary purposes. As it has been found an efficient agent for the decomposition of so stable a substance as iodide of potassium, it can hardly be doubted that it will also effect the oxidation of any animal or vegetable substances, particularly those which are in course of putrefactive decomposition. It has also the property of being capable, after having once performed its measure of oxidation, of forming a new amount of active peroxide of hydrogen, which may be made available for further work. Several experiments, made by Mr. Kingzett, prove that this oil is a powerful antiseptic. Beef put in water containing it was kept sweet during periods of twenty-five and forty days; flour paste from thirty to fifty days; the white of eggs for fifty days; wine for one hundred days. The oil is not destined to supersede the sanitas, for it is too powerful in its action to serve the purpose to which the aqueous solution is applied, and is not adapted to meet the same ends, but be a valuable supplement to it. It may be added to glycerine, oils, or ointments, when they are applied to the body in cases of infectious disease. It may be evaporated for the fumigation of rooms which have been occupied by persons suffering from communicable diseases. Plane surfaces, as floorings and walls, may be disinfected by wiping them with a cloth or brush which has been dipped in the oil; and only a small quantity of oil is necessary for this purpose, for it spreads freely. It is slowly volatile, and may be used as an aërial disinfectant. The emulsion in water may be applied in a great many places; and sprinkled over sawdust it may be employed as an effective deodorant.

The Color-Sense among Uncivilized Peoples.—Dr. Hugo Magnus, of Breslau, has just published a work containing the results of inquiries which he has made into the power of uncivilized people to distinguish colors. He sought to ascertain from direct evidence the extent to which the color-sense already exists among savages, and how great is its capacity for development, and to collect the terms by which they express their distinctions of color. He prepared a set of questions relating to the most marked colors, such as black, gray, white, red, orange, yellow, green, violet, and brown, omitting those shades to distinguish which some degree of education is obviously necessary, and sent them to physicians, missionaries, merchants, and other persons in different parts of the world having intercourse with native races, who seemed able to afford information on the subject. As a whole, he has found that the color-sense of the ruder nations is circumscribed by limits differing but little from those which bound the same sense among civilized people. In no race did he find an entire absence of the faculty of distinguishing between the principal colors. Taking red, yellow, green, and blue, as the chief representatives of the colors of the longer and shorter wave-lengths, there was not one among the tribes coming within the range of the inquiry which did not show some knowledge of these four colors. This knowledge must be considered as only relative, and not as existing in the same degree among all tribes. Savages exhibit important differences in the degree to which their sense of color is capable of cultivation. Some show considerable skill in distinguishing between different mixed and transitional colors, others are less keen to perceive transitional colors, while there are some who are slow in marking the most distinct principal colors without being wholly incapable of it. This dullness is shown chiefly in reference to the colors of the shorter wave-lengths, as green, and more especially blue. There are tribes which have surprisingly little knowledge of these colors; among them are some of the aboriginal tribes of southern India, whose color-sense is developed only to the perception of red, while their knowledge of yellow and green and blue is most limited and rudimentary. The inhabitants of the island of Nias have one name for blue, violet, black, and green, another for yellow and orange. Numerous observations are cited to prove that the capacity to discriminate between the colors of the longer wave-lengths is sharper than that relative to those of shorter wave-lengths. An English consul in the Loyalty Islands informs Dr. Magnus that the inhabitants of that group understand the differences between colors very well, but confound them in naming them. The negro tribes of Sierra Leone, distinguish between the several colors, and have words to indicate them. Gray and orange are least regarded, and are spoken of as white and red. Blue and green are frequently confounded, but are seldom mentioned as identical. The pastoral Ovahereros, or Damaras, of South Africa, are keen in their appreciation of the shades of color that are marked on their cattle, and have names for all of them, twenty-six terms in all, but have no names for the colors that are not cattle-colors, although they know them apart quite clearly, and will use foreign words in speaking of them if it is necessary. Sometimes, for lack of a better word, they will use their own word for yellow, for blue, or green, but with a clear sense that they are applying it inaccurately. Most of the Damaras have come into some contact with civilization, but no important difference in the capacity to distinguish colors can be found between the civilized and the uncivilized members of the race. The uncivilized, however, although they know them well enough, can not give names to blue and green, and think it strange that these colors should need names. A tribe on the Gold Coast are well acquainted with the difference between red, yellow, green, and blue, but are wholly destitute of terms for the colors of the medium and shorter wave-lengths, and seem to have names only for white, black, and red. Virchow found similar conditions to exist among the Nubians, who were lately in Berlin, and a similar indifference to the colors of the middle and shorter wave-lengths to prevail among them. Most of them were accurate in perceiving and naming the four higher colors of the scale, and black, white, gray, and red, but recognized the other colors with some difficulty. Professor Delitzsch has remarked that the people of the ancient Semitic races had little appreciation of blue. This dullness in distinguishing the colors of the shorter wave-length contrasts strikingly with the sharpness which people of all races display in distinguishing and marking red.

Slaughter of Food-Animals among the Jews.—According to the analysis of Dr. Rabbinonicz, of Paris, the Jewish Talmudic rules concerning the slaughter of food animals were framed with the special object of providing for the infliction of the least possible suffering upon the animal, and of procuring the meat in the most wholesome condition for food. They prohibit the stunning of the animal by a blow on the forehead, because it is far from certain that the blow immediately annuls pain, and it is certain that it does not annul it if inflicted by an awkward hand. The rules require that the act of killing shall be performed by the sweep of a long, sharp instrument, which shall at once sever, more or less completely, the trachea and œsophagus. They do not require the arteries to be cut, for the nature of those vessels was not known when the rules were made, but the arteries and the important nerves around their sheath are cut in practice, and the animal speedily faints into insensibility, and dies of hæmorrhage. The important points of the code are, that the steps in slaughter shall be continuous, because any interruption, however minute, in the process, is likely to prolong the sufferings of the animal and make it unfit for food; that the cut shall be made by a to-and-fro stroke, without any pressure beyond what is required to carry the knife down to the necessary depth; that the incision in the skin shall accurately coincide in length with the deeper portion, so as to leave no "tail" to the wound; that the wound shall not be made so high as to risk contact of the knife with the bony structures above the cartilaginous rings of the trachea, for this would be likely to cause preventable suffering to the animal, and compel the rejection of its flesh as food; and that no tissue should be torn or jagged. The candidate for a license to slaughter has to go through a long course of preparation, of which a kind of rough anatomy forms a part, and afterward to prove his competency to the satisfaction of the appointed authorities. The heart is also carefully examined, to ascertain whether it is fit for food. The rules on this subject, although made before anything was accurately known of pathology, contribute, as a whole, to the selection of that which is good and to the rejection of that which is bad. The use of the blood is forbidden, and it is in the blood that science to-day tells us the germs and the matters that are detrimental are most likely to be found and to be most active. The lung is the organ most diligently searched and severely tested; and it is the lung which is most liable to disease, and in which, when disease is present, it is most obvious. Fewer directions are given concerning search for morbid conditions in the other organs, "for, as it was known that animals were but rarely perfectly sound in their entire system, a more rigid search would have been nearly tantamount to depriving the people altogether of animal food. But, although a search for other diseased organs is not enjoined, any morbid condition observed by the practiced eye of the slaughterer insures the rejection of the animal as food."

The Origin and Progress of Pisciculture.—M. Ph. Gauckler, in a recent work on fresh-water fishes, has reviewed the history of pisciculture from the earliest times to the present. In modern times, Dom Pinchon, a monk of the Abbey of Réome, in the fourteenth century, hatched fish in boxes through which a current of water was kept slowly flowing. The Chinese practice of placing limbs of trees or herbs in the spawning-places to collect the eggs has been in vogue from time immemorial in Europe, chiefly in the ponds of Bohemia. A Swedish magistrate named Lund, of Linköping, adopted it successfully in 1761, after having casually remarked that eggs which clung to juniper-branches did better than those which fell to the ground. In 1834 Mauro Rusconi, an Italian, successfully propagated the tench, the bleak, and the perch, in the lake of Como; and MM. Agassiz and Vogt began at about the same time their embryological experiments on the Salmonidæ, with the view of multiplying one of the species in the lake of Neufchâtel. Mr. John Shaw, of Drumlanrig, adopted artificial culture to increase the product of the salmon-fisheries of the river Nith, in Scotland. His example was followed by Lord Gray, on the Tay, in 1838, and by others in 1841. Joseph Remy, of La Bresse, in the Vosges, made his first experiments in artificial reproduction, having, by his own investigations, discovered a process of which Jacobi had given an account, but which had not attained publicity eighty years before. M. Coste, of the College of France, perceived the importance of this discovery and adopted it in 1850, while he secured a suitable reward to Remy. The attention of several persons in France was directed to pisciculture by the enthusiastic publications of M. Coste, and the experiments of M. de Quatrefages and other members of the Society of Acclimation. They were encouraged by the gratuitous distribution of eggs and fry, which were liberally furnished to French and foreign customers from the establishment of Huningue. During the later years of the French administration, the quantity distributed amounted to twenty millions a year for species of the salmon family only. The business of propagation has been extensively carried on in England as a commercial speculation. Since 1854 the Messrs. Ashworth have put 260,000 salmon in Lough Corrib, Connaught, Ireland. A special establishment has been erected at Perth, and Cooper's fish-ladders have been put in all the rivers frequented by salmon. Important establishments for the artificial propagation of salmon have been created in Holland. The basins of the Zoölogical Garden of Ghent and of the Horticultural Society of Brussels have been adopted for purposes of hatching. Several lakes in Switzerland have been largely restocked by artificial means. The most practical results, according to M. Gauckler, in the perfection of processes, have been gained in America, and acknowledgment is freely made of the value of the labors of Baird, Livingston, Stone, Ainsworth, Seth Green, Collins, Mather, and others, in bringing down the science from the domain of speculation to that of palpable facts and remunerative results.

Sanitary Protection Associations.—Sanitary protection associations have recently been formed in Edinburgh and London, the objects of which, as stated in the prospectus of the London Association, are: 1. To provide their members, at moderate cost, with such advice and supervision as shall insure the proper sanitary condition of their own dwellings; and, 2. To enable members to procure practical advice, on moderate terms, as to the best mode of remedying defects in houses of the poorer class in which they are interested. The associations are not intended as a substitute for a municipal inspection, or to conflict with the public authorities, but to supplement their action. The idea of the associations originated, according to the statement of Professor Fleeming Jenkin, the founder of the one at Edinburgh, in a paper read by him before the Society of Arts, in his endeavoring to explain in a lecture the principles of sanitation, so that they could be applied practically by householders. He found that he could not do it, but that, after all his efforts to make the matter clear with general demonstrations and diagrams, professional advice had to be sought by each householder for his own particular case. What advice could the public obtain? The plumber and builder were interested parties, and not always competent; engineers held their services at too high a rate to be readily accessible to the majority; public officers could not be called upon unless there was probably some actual serious defect to be remedied. The thought occurred that an association of householders might be formed, to employ an engineer, at a fixed salary, who should make an inspection, draw plans, and propose improvements, for each subscriber, at an expense to the latter only of his annual subscription. The subscription to the Edinburgh Association was fixed at one guinea a year. The sum has been found enough to answer the intended purpose, and the work has been conducted with entire satisfaction and success in that city for three years. The London Association requires an entrance-fee of two guineas for houses of less than four hundred pounds rental, and subsequent annual fees of one guinea. A person joining either association and paying the entrance fee obtains all the privileges of membership for a year without committing himself to any further payments. He has a right to a thorough professional inspection of all the water and drainage apparatus in his house, including every pipe, tap, cistern, and sanitary convenience, for efficiency, leakage, smells, and ventilation, and the main drain between the house and the town sewer, the opening of which, however, is at his expense. As soon after the inspection as may be, he may receive a detailed report, describing the condition of his house, accompanied by a sketch diagram showing every pipe and trap, in connection with which recommendations for improvements are made when necessary, with rough estimates of the probable cost if they are desired. The wishes of the occupier are taken into account, the more important are distinguished from the less important alterations, and the suggestions are specific enough to enable the occupier to consult intelligently with his plumber or builder on the subject. The society has no interest in recommending any expenditure, and the occupier has his option whether he will incur any or not. If he concludes to have the work done, he may have it inspected, when it is completed, or nearly so, and obtain a Certificate as to the sanitary condition of his premises. The second year's inspection is a simpler matter than the first year's, for it is guided by the results of the previous inspection, and has to be only comparative. With respect to the efficiency of this system, Professor Jenkin says that it has been shown that the required services can be rendered in a thorough and efficient manner by one resident engineer, for four hundred and fifty or even five hundred houses in one year. Twelve hundred houses have been put in order in Edinburgh, and there has not been during three years one case of complaint that the houses were not thoroughly examined, or that the reports were not sufficiently detailed; but, at the annual meetings of the society, member after member has arisen to express his satisfaction at the work.

Dust, the Nucleus of Fog.—According to the researches of Mr. John Aitken, as described in a paper read by him before the Royal Society of Edinburgh, the formation of fogs and clouds is dependent on the presence of dust in the atmosphere. His view was illustrated by an experiment in which steam was mixed with air in two large glass receivers, one of which was filled with common air, the other with air that had been filtered. Clouds appeared in the former vessel, while the air in the other one remained perfectly transparent. Similar results attended an experiment with the air-pump, in the receiver of which a little water was placed to saturate the air. On removing a part of the pressure, a fogginess appeared, or nothing was visible, according as the air in the receiver was unfiltered or filtered. From these and other similar experiments, Mr. Aitken has concluded that, whenever water-vapor condenses in the atmosphere, it always does so on some solid nucleus; that dust-particles in the air form such nuclei; that if there were no dust, there would be no fogs, no clouds, no mists, and probably no rain; that the supersaturated air would convert every object on the surface of the earth into a condenser on which it would deposit; and that our breaths, when they became visible on a cold morning, and every puff of steam as it escapes into the air, show the impure and dusty condition of the atmosphere. Experiments with other vapors than that of water showed that their condensation is governed by a similar rule. The condensation is not produced by any particles which we can see, or even by those which are revealed by the sunbeam, for these may be driven off by heat and the fogs still be visible, but by vastly more numerous, infinitesimally small, and invisible particles which heat will not drive away. These particles may be furnished by the spray from the ocean, by meteoric matter, by the operation of almost every force. The products of all kinds of combustion give rise to them. The use of purer forms of coal, or even of gas, does not avoid them, nor even appear to diminish their number. Common salt is one of the most active fog-producers, but the products of burned sulphur exceeded in this respect all the other substances experimented upon. The density of the fog depends on the amount of fine dust in the air. If only a few particles are present, only a few fog-drops form, and they are heavy and fall like rain; if there are many, the more dust the finer are the fog-particles, and the longer they remain suspended in the air. Though the use of more perfect forms of combustion is not likely to prevent the generation of fogs, it will, by preventing the accumulation of smoke which now comes down into fogs and mixes with them, remove the cause which makes them so dark and extremely annoying.

Electric Lights for the French Coasts.—M. E. Allard, Director of the Central Lighthouse Service, has submitted to the French Minister of Public Works propositions for lighting the coasts of France with the electric light. He would begin by substituting the electric light for the present oil-lights in forty-two of the principal lighthouses, and adding sound-signals in twenty of them. The mean range of visibility of the present oil-lights is twenty-two miles on the ocean-coast and twenty-seven miles on the Mediterranean coast. Within these radii they can be depended upon as signals during one half of the year; during the other half of the year they are liable to be interfered with by unfavorable atmospheric conditions, so as to greatly reduce their radii of visibility. With electric lights having the powers that M. Allard proposes to apply, the period during which the penetrative power may be deficient will be reduced to sixty days, or one sixth of the year on the ocean, and to twenty-four nights, or one fifth, on the Mediterranean coast. The cost of the proposed changes is estimated at seven million francs, or eight million francs if sound-signals are also provided. It is believed that the cost of keeping up the light after the change is made will be several times less than that of maintaining the oil-lamps.