# Popular Science Monthly/Volume 21/October 1882/Popular Miscellany

POPULAR MISCELLANY.

The American Association.—The meeting of the American Association for the Advancement of Science, at Montreal, which closed August 30th, was, in every respect, one of the most successful meetings in the history of the society. The attendance—nine hundred and fifty members—was but little short of that registered at Boston two years ago, and constituted it one of the large meetings. Three hundred and twenty-five new members were elected, and more than two hundred and fifty papers were accepted. The meeting was opened on the 23d of August, with a brief address by the incoming President, Dr. Dawson, of Montreal, who spoke of his (a Canadian's) election to the presidency as significant of the society's extension over the continent, and its disregard of national boundary-lines. Dr. T. Sterry Hunt, who followed the president as the especial representative of the city of Montreal, also spoke of the expansion of the society, and expressed the hope that it might yet meet in the city of Mexico, as the French had already carried their "war of science" into Africa, at Algiers. The nine sections into which the Association is now divided w T ere severally opened with addresses by their respective presidents. Professor Bolton, in the Chemical Section, spoke on "Chemical Literature"; Professor Harkness, in the Mathematical and Astronomical Section, on the transit of Venus. Professor Brush, the retiring President of the Association, gave as his official address the comprehensive review which we publish in the present number of "The Popular Science Monthly," of the "Progress of American Mineralogy." Dr. Asa Gray gave an address on the "History of the Study of the North American Flora," and expressed the hope that the work of examination and classification might be completed in his lifetime, if it could not all be guided by his hand. The other papers were too numerous to be even catalogued here. We mention only a few, which seem to be of general importance or interest. They are those of Professor Mason, unfolding a scheme of anthropology; of Dr. John Rae, of London, on "Arctic Explorations and Ethnology"; of Commander Bartlett, on "The Gulf Stream"; of Mr. Franklin B. Hough, on "Plantations of the Eucalyptus"; of the Rev. Dr. Houghton, of Dublin, embodying a new theory of the evolution of the planets; of Professor Cook, of New Jersey, on "Evidences of Coast Depression"; of H. Carvill Lewis, on "The Great Terminal Moraine across Pennsylvania"; of Professor Newberry, on "The History of Plant-Life in America"; of the Hon. Horatio Hale, of Clinton, Ontario, on "Indian Migrations as evidenced by their Language"; and of Mrs. Erminie Smith and Miss Alice C. Fletcher, on topics relating to Indian ethnology. Excursions were made to Quebec, Ottawa, and other places. Several visitors of distinction were present from abroad. Among them, besides those already named in connection with their papers, were Professor W. B. Carpenter, of London, who read a technical paper in the Microscopical Section; Dr. Valdemar Kovalevski, of Moscow; Dr. Koenig, of Paris; Mr. Fitzgerald, of Dublin; and D. Szabo, of Buda-Pesth, Hungary, who had a paper in the Chemical Section. A good financial exhibit was made, with the announcement of generous special gifts. A memorial to Professor Rogers was determined upon. The Association decided to hold its meeting for 1883 at Minneapolis, Minnesota. The following officers were chosen: President, Professor C. A. Young, of Princeton; vice-presidents of sections: Mathematics and Astronomy, W. A. Rogers, of Cambridge; Physics, H. A. Rowland, of Baltimore; Chemistry, E. W. Morley, of Cleveland; Mechanical Science, De Valson Wood, of Hoboken; Geology and Geography, C. H. Hitchcock, of Hanover; Biology, W. J. Beale, of Lansing; Histology and Microscopy, J. D. Cox, of Cincinnati; Anthropology, O. T. Mason, of Washington; Economical Science and Statistics, F. B. Hough, of Lowville. The purpose of the British Association to hold its meeting for 1884 in Montreal was announced.

Scientific Forestry.—There is no mystery in the scientific cultivation of forests, so far as concerns the tillage of the crop. All that is needed is to observe the action of nature in the forest, and follow it, or utilize it advantageously, when that can be done. The object of the cultivation should be to obtain the utmost possible advantage from the soil by keeping it always covered with a growth of trees; and, when the trees arrive at maturity, to remove them in such a manner that the smallest possible interruption may be caused to the productive work of nature. When the time has come for the removal of the timber, the ground should on no account be anywhere all cleared of trees at once; but a commencement should be made by felling a tree here and there, and so breaking the thick cover of the forest as to allow sufficient light and air to reach the ground, and cause the seed which has fallen to germinate. In this w r ay about one fifth of the mature trees should be removed every five or six years, never by making large gaps in the cover, but taking a tree here and there, and always leaving the finest and most vigorous trees till the last, so that in about thirty years the whole of the old trees will be cleared off, and a new forest established in their place. Thus the seeding of the wood will be effected by the agency of the finest trees, which will be themselves all the while increasing in bulk, and the productive power of the soil will be utilized to the fullest possible amount. It is not only in the removal of the timber and the reproduction of the forest that we ought to study the action of nature, but it is equally necessary that we should do so in the felling for improving the growing crop, or, as it is commonly called, the thinnings. The competition between trees after they reach their full height, at half their full age, is for space to spread their heads; and from this time, till they arrive at maturity, they go on always augmenting the diameter of their stems, but at the same time decreasing in number. It is calculated that, if sixteen hundred trees of four inches in diameter can stand and thrive on an acre of ground, there will not be more than four hundred of them when the trees have grown to eight inches, two hundred when they have reached twelve inches, and between one hundred and one hundred and forty when they have attained sixteen inches in diameter. Little is to be done in the earlier stages of a forest's growth except to keep the heads of the most valuable species from being overtopped by those which stand near them: and this can be done best, not by removing the others, but by cutting off or breaking the. tops; for it is desirable at this stage, for the sake of the natural pruning, to have the trees growing as thickly together as possible. At a later stage, thinnings can be judiciously arranged so as to pass through the entire forest at intervals of from ten to fifteen years, enabling the whole area to be operated on in turn. In executing these, the most difficult of all forest operations, it will be well to remember that the object is to give room to the heads of the trees, and not to their stems; for the stems will never be too close together as long as the heads have room properly to develop themselves. The favoring of the most promising trees, and the removal of the weaker ones, together with the preservation of continuous shade to the surface of the ground, while all the trees have sufficient room to grow, should be the particular ends aimed at.

A New Plan for Armored Vessels.—The Naval Committee of the United States House of Representatives has given favorable consideration to a new plan for building armored vessels which has been devised by a retired invalid engineer. The principal armorial application consists of a submerged "turtle-back," about four inches thick, and extending from side to side and from stem to stern of the vessel and below the waterline, so arranged that an enemy's shot from any direction can hit it only at a deflecting angle, so as to be thrown off rather than go through. The sides of the vessel above the turtle-back are filled in with cotton or cork, in which a breach made by the passage of a ball will be self-closed by the elastic action of the substance. They may, moreover, be shot to pieces without destroying the buoyant power of the ship. The guns are mounted upon heavy, impenetrable, centrally arranged, cylindrical armor, which extends to the bottom of the ship, and is there seated on an hydraulic cushion. The breech of the gun is also inclosed in an oval armor, so arranged as to deflect a ball, striking it from any point, in a harmless direction. The gun is operated by an hydraulic loading apparatus, which is worked by one gunner, and hydraulic buffers are provided to take up the recoil.

The Timber-Line of Mountains.—Mr. Henry Gannett, noticing, in "The American Journal of Science," Dr. Rothrock's statement that, as a whole, there is little or no increase in the altitude of the timber-line toward the equator in the Western hemisphere, south of the forty-first parallel of north latitude, observes that the height of the timber-line is purely a question of temperature, and that that is a function of the latitude, the elevation, and the mass, of the country in the neighborhood. A great mass of country, if raised to a considerable height above the sea, carries with it the isothermals. Therefore, in considering the height of the timber-line, "we must regard the mountain-ranges in connection with the plateaus on which they stand, their latitudes, heights, and masses, or what, in a measure, sums up these three, their temperatures, as it is by these that its height is determined." The actual elevation above sea-level of the timber-line in the Cordilleras of North America ranges from six or seven to twelve thousand feet. It is lowest in the Coast and Cascade Ranges of Washington Territory, and rises as we go southward through Oregon and California. On the high Sierras of Eastern-Central California, forests grow to 10,000 or 12,000 feet, while the ranges of Southern California do not reach the upper limits of forests Few of the ranges of Nevada reach the timber-line, which varies from the height of 9,000 feet in the northern to probably 11,000 feet in the southern part of the State. In Arizona, probably none of the mountains reach the timber-line except the San Francisco group and the Sierra Blanca, where the line is at 11,000 and 12,000 feet. In New Mexico, the line averages about 12,000 feet above sea-level, and the higher annual temperature of the southern part of the Territory is fully compensated for by the greater altitude of the plateau in the northern part. In Colorado, the line rises from 11,000 feet in the northern to 12,000 feet in the southern part of the State; in Wyoming, from 10,000 to 11,000 feet in the Wind River and Teton Ranges, to about 11,000 feet in the Park Range; in Montana and Idaho, it ranges at from 9,000 to 10,000 feet, and in the Uintah and Wahsatch Ranges of Utah it is at about 11,000 feet. It is evident, if these considerations hold good, that the upper limit of timber must have approximately the same mean annual temperature everywhere. This temperature can not be measured directly for different places, but may be estimated by calculation by taking the mean temperature at some base in the neighborhood, and allowing a degree of fall for every three hundred feet of additional elevation. A calculation made on this basis for thirteen mountains, including Mounts Washington and Marcy, and several Western peaks, gives a mean of 30.4°, the extremes being 28° and 33°.

The Soil and Scarlatina.—Dr. Eklund, of Stockholm, Sweden, has for several years devoted much time to the pathology and etiology of scarlatina, and has reached conclusions of high practical importance in the light they throw upon the connection between bad drainage and other insanitary conditions and outbreaks of that disease without actual infection. He has constantly found a prodigious number of discoid bodies in the urine-of persons suffering from scarlatina, and most positively asserts that he has also noticed those identical organisms in vast numbers in the soil and ground-water of the Isle of Skeppsholm; in mud from the trenches, dug for the watermains; and among the greenish molds of the walls of the old barracks, where scarlatina was most rife. He furthermore alleges cases of scarlatina occurring in children after drinking milk mixed with the ground water of the island, and one case which followed an immersion in one of these trenches, and the drying of the child's clothes in a small room. In still another case scarlatina broke out in a block immediately on the exposure of the ground-water by excavations around. These observations, however, and those of other persons who have found micrococci in the animal fluids in scarlatina, even if the organisms are observed to be invariably present, can not be held to prove that they are the cause of the disease till the fact has been directly verified by inoculation into a healthy body carefully isolated from all other sources of infection.

Lip-Teaching for the Deaf and Dumb.—Earl Granville, as President of the Association for the Oral Instruction of the Deaf and Dumb, had occasion recently, at a meeting in behalf of the system, to remark upon the satisfactory progress that had been made in lip-teaching, by which the deaf were placed in a position to converse with their fellow-creatures without the aid of signs. The number of pupils in the association's school had increased, and favorable reports had been received from the class of the School Board of London. Except where idiocy or mental incapacity existed, this method of teaching was applicable to all cases. Its advantages had been acknowledged in a remarkable degree at a conference lately held, where a consensus of opinion was expressed in its favor. In evidence of the great benefits the system conferred upon persons trained under it, Earl Granville mentioned that several former pupils of the school were present who were now earning their living in positions which they would hardly have obtained had they been educated by the system of signs. An examination was afterward had of pupils of the training college and school, in which they showed that they understood, by watching a speaker's lips, what was said to them, and could make intelligible replies to it.

Chaldean Astronomy.—The invention of astronomy is ascribed to the Chaldeans by some ancient writers. It is said that a certain Zoroaster, King of Bactriana, was the first who observed the stars, about 1700 b. c.; although, according to Porphyry, Calisthenes found at Babylon and sent to Aristotle a series of observations going back to the earlier date of 1903 b. c. As yet, however, the Chaldean observations with which we are acquainted are reduced to the account of three eclipses of the moon that took place about 719 b. c. Hopes were entertained, when the discoveries of cuneiform tablets were made in the ruins of Babylonia and Nineveh, that trustworthy information of the real condition of astronomical science among the Chaldeans might be gathered from them; but it was some time before anything of this kind was realized. Messrs. Oppert and Sayce, it is true, found a few astronomical documents in the library of a king of Assyria, but they contained more astrology than astronomy, and were, moreover, too badly preserved to be of much use. Quite recently the Assyriologue, Father Strassmeyer, of the Society of Jesus, has found a few documents relative to astronomy in the Spartoli collection of the British Museum; and these have been carefully examined by Father Epping. They indicate that the Chaldeans had considerable knowledge of astronomy. Besides calculating the time of the new moon, and taking account of the thirds in their observations, they followed the courses of the planets, were acquainted with the retrograde movement of Mars, and referred the positions of the planets to those of the stars. If other results similar to these are at all extensively obtained from the immense amount of study yet to be made of the tablets, astronomers may hope to acquire materials of extreme value for the verification of their tables and the study of the system of the world.

Pedigree Selection in Food-Plants.—Major Hallett, in commending before the Brighton Health Congress his "pedigree system" for the improvement of food plants, takes notice of the immensely greater advantages in favor of systematic improvement afforded by plants over animals. A cow or ewe, he says, "produces at birth one (or two) only; a single grain of wheat has produced a plant the ears of which contained 8,000 grains, all capable of reproduction. Now, we can plant all of these, and of the resultant 8,000 plants reserve only the best one of all, to perpetuate the race, rejecting every other." The principle of Major Hallett's system consists in applying this rule, of reproducing only the best plants of each lot in successive years. "Can anything approaching such a choice as this," he says, "be afforded any breeder of cattle or sheep, no matter how extensive his herd or flock?" Cereals, improved by Hallett's system, have now been cultivated in more than forty different countries in Europe, Asia, Africa, America, and Australia, with complete success everywhere, so far as reports have been received. A parcel of pedigree wheat taken to Perth, Western Australia, in 1862, where the average crop was ten bushels to the acre, produced from twenty-nine to thirty-five bushels to the acre, with seventy-two as the largest number of heads on one stool, and one hundred and thirteen grains in the largest ear. In 1881 the same wheat, or its descendant, produced, in New Zealand, seventy-two bushels on one acre; with more than ninety ears, some of them containing as many as one hundred and thirty-two grains each, on single plants. The same return—seventy-two bushels to the acre—was reported cf three acres in Essex, England, in 1876, with one hundred and five ears, containing more than 8,000 grains, on one plant. Reports corresponding with this have been received from Brussieres, France; Linlithgow, Scotland; Russia, Hungary, Italy, Holland, Denmark, and Sweden. The Hallett wheat withstood the frosts of 1875 and 1876 in Belgium, when other varieties were killed. In India, Sir Seymour Fitzgerald, Governor of Bombay, in 1870, reported the crop from the pedigree wheat to be fifty per cent greater in quantity and fifty per cent more valuable in quality than that produced from the best other seed that could be bought in the market. The same success has been obtained with barley and oats cultivated after this system. A friend of Major Hallett's, in Italy, applied his system to the sugar-beet, with the result of obtaining, after seven years of improvement, three times as much sugar and wine from the same acreage of roots as he had been accustomed to get at first. Experimenting with the potato, Major Hallett has started each year, for fourteen years, with a single tuber, the best of the year, cultivating for freedom from disease and for productiveness. Dividing the first twelve years of the fourteen into periods of four years each, he obtained for the first period an average of sixteen tubers from each single best seed-tuber; for the second period, nineteen; and for the third period, twenty-seven, or nearly double the yield of the first period. This plan of selection is on trial, in India, for cotton, and the reports so far received show already a marked difference in its favor.

The Mound-Builders in Mexico.—Mr. F. F. Hilder, in a paper on "The Archæology of Missouri," summarizes the results of the efforts of Mr. S. B. Evans to follow the works of the mound-builders down the Mississippi Valley, and connect them with the ancient works in Mexico. Beginning in Minnesota, Mr. Evans has, by personal survey, found an unbroken chain of these works along the great river to the Gulf, with colonies on the principal tributaries traversing the States that border on that stream. "Mounds were found along the entire route, and on the shores of the Gulf. Crossing into Mexico, the chain, dropped in the sea at Galveston, was recovered near Vera Cruz. On the plain of Cholula is a mound that, if transferred to Cahokia, would fit the landscape, and appear in general keeping with the works. On the other hand, if the great mound of Cahokia were brought in presence of Popocatepetl, it would not be abashed, but would be a fit companion of the pyramid. The pyramids of the sun and moon at Teotlihuacan would be mounds in Virginia and Ohio; and the great mounds of Grave Creek and Selzertown might embellish the 'ancient city of the gods.' Excavations were made in Mexican mounds, as they were made in the United States, and substantially the results were the same."

Elephant-Service in Africa.—Mr. L. K. Rankin, of the Belgian Elephant Expedition in Africa, has made a statement of the probable value of the practical service that may be expected from elephants if their introduction as carriers is attempted in that continent. When the expedition reached Mpwapwa, a report was drawn up to be sent to the King of the Belgians, which stated that "the elephant expedition has now been proved a complete success." This assertion was justified by Carter, the head of the expedition, now deceased, on the three counts of—1. The immunity of the elephants against the tsetse-fly after twenty-three days of exposure to that insect; 2. Their maintenance during one month mostly upon the uncultivated food of the country, and therefore at little cost (only about twenty-five rupees, or fifteen dollars, for four); and, 3. Their ability to march over all kinds of ground, soft, stony, sandy, boggy; to conquer all eccentricities of topography—hill and dale, river and jungle—while laboring under double their due weight of baggage, some fifteen hundred instead of seven hundred pounds; and this in a style that no other beast of burden could hope to emulate. This brilliant forecast received a seeming bitter contradiction in less than a week, when the largest and most valuable elephant, returning from a day's expedition, in apparently good health, suddenly lay down and died. Mr. Rankin believes that the death, which was followed shortly afterward by that of another elephant, was caused by exhaustion brought on by imposing too heavy loads and too severe labors upon the animal, combined with too great a change from the strong food it had enjoyed in India to the wild grasses of Africa. The animals had been stall-fed in India, "on the fat of the land," while in Africa they were turned out to forage for themselves, and very little corn and rice was bought for them. Whereas, according to Sanderson, seven hundred pounds is the limit-weight an elephant should carry on flat ground for a prolonged time, these animals bore at first twelve hundred, then fifteen hundred, and at one time seventeen hundred pounds; while they daily climbed the most tremendous hills. These views are enforced by the fact that, while the elephants were fat and round at starting, they had lost so much flesh by the time they reached Mpwapwa, that their backbones stood up six or seven inches from their flanks! These facts resulted from faults in management, in insufficiency of preparations for the expedition, and mistaken views of economy, and should not be allowed to prevail against the competency of elephants, under good management, to endure reasonable service, on which hardly any doubt is thrown. Dearly bought experience, Mr. Rankin suggests,-would another time remove the risks that were incurred; and he has not the shadow of a doubt that there is yet a great future in Africa for the elephant, especially when the stage of capturing and taming the native species has been reached.

Co-operation of Medical Officers and People in Sanitary Objects.—The Sanitary Aid Association of St. Leonard's and Hastings, England, during nine years of work among a population of thirty-five thousand, has secured a co-operation between the people and the sanitary officers, under which the spread of all infectious diseases has been effectually prevented. This it has done by tact in the exercise of its functions as a medium between the medical officers and the people. It seeks, first, to guard against popular jealousy of inquisitorial inspection. The teachers of the schools are expected to make weekly returns of all absentees, with the cause of absence if known; if the cause is not known, some fit person is deputed to make a friendly casual visit to the family, without any suggestion of suspicion of fever, and report the information received to whoever acts as sanitary manager. The case is then put into the hands of the health officer, and his endeavors are furthered by explaining to the mother that she shall receive, for the strict performance of the processes of disinfection taught her, assistance, to be allotted according to the circumstances of the family. The assistance may come in the form of a milk allowance, beef-tea, wine, or whatever may be ordered by the medical attendant, a nurse, or a person to do the washing, or, where no want exists, of little delicacies and comforts which may be given without offense. It should always be connected with Obedience, by the persons assisted, of the inspector's orders, and should be accompanied, through the period of illness, by the promise of suitable help at the end. The greatest difficulties the medical officers have to meet arise from the desire of the poor to conceal their cases, for fear of injuring their business; but, under the operation of this system, every family that enjoys the benefit of its application and finds out what help and relief it gives tells the neighbors, and so it is brought about that the medical officer becomes himself the poor man's accepted friend. The St. Leonard's and Hastings society has never incurred a failure during all the years of its working; yet so unobtrusive have been its operations that one who should go down to inquire at random about it, without having a list of its allies, would have difficulty in discovering its existence. By adhering to and avowing the principle that it has no more right to interfere with the persons it visits than they with its members, by using persuasion and sympathy instead of threats, it has reduced the number of unmanageable cases to one a year; and has always brought even these around by taking care in conversing with the persons to give full information respecting disinfection. Thereupon, they turn around and act upon the information they have gained, so as to show how well they can do without their visitors.

Number of Species of the Orang-Outang.—The number of species of the orangoutang has been placed variously at from one to four. The upholders of the one-species theory have doubted whether the characteristics that were regarded as indications of specific differences might not really have arisen from the examination of skulls of different ages. To contribute to a solution of this doubt, Mr. Frederick A. Lucas has examined the large collection of orangs of Professor Henry A. Ward, and compared the notes taken by Mr. William T. Hornaday, while collecting orangs, and has satisfied himself that the views of the advocates of one species are correct. He previously believed that there were two species. He adds to his notes on the subject the suggestion that "they point clearly to the fact that it is extremely dangerous to form a species from observations of one or two skulls," and that they render it very probable that many fossil species have been based on individual or sexual peculiarities.

The Law of Land Formation on our Globe.—Professor Richard Owen, of New Harmony, Indiana, has observed some coincidences in the arrangements of continental lines and in the location and direction of elevations and depressions of the surface of the earth, which have suggested to him a law. by which dry land shows itself above the ocean, which he believes to be of almost universal application to geographical and geological phenomena. The coincidences which he describes may be traced by any one on a globe or a large map. The law, as Professor Owen has stated it in a paper on the subject presented to the American Association last year, is, in general terms: "The land on our globe shows itself above the ocean-level in definite multiple proportions, by measurement; the unit is the angular difference between the axis of revolution and the axis of progression. For convenience, as that angle has been lessening for centuries, we might call it 24°. We then have:

 Geographical and geological unit ${\displaystyle =}$ 24° ${\displaystyle =}$ 360°15 Greatest width and length of continents ${\displaystyle =}$ 3 x 24° ${\displaystyle =}$ 72° ${\displaystyle =}$ 360°5 Radius for continents ${\displaystyle =}$ 36° ${\displaystyle =}$ 360°10 Half radius ⁠" ${\displaystyle =}$ 18° ${\displaystyle =}$ 360°20

The measure for oceanic distances is the complement of 24° ${\displaystyle =}$ 66°. The ratio of land to water, as shown by Professor Dana, is as 100: 275. The ratio of 24°: 66°:: 100: 275. All measurements are to be estimated at the equator.

Regarding his law in detail, Professor Owen finds, first, that many longitudinal elevations and depressions on the earth's surface (the result apparently of cooling and contraction), especially near the greatest median—north and south—extension of each continent, coincide with some meridian. This shrinkage has caused a north and south continent to appear in each of the four quarters of the earth, going around on the equator. Minor north and south extensions can be traced at intervals, often of 412° or 9° apart all around the globe, alternating usually with trends which form with them angles of 2312°. In verification of this law, adjust the globe so that the poles shall be at the wooden horizon and the eastern extremity of Brazil at the brass meridian. Then we shall find the two Americas occupying one, Europe and Africa the second, Asia and Australia the third, and North and South Oceania the fourth, of the quarters into which the rules divide the globe. It will be found that great elevations are matched by depressions on the opposite side of the globe, as the Himalayas and Central Asiatic table-land with Hudson Bay, the American lakes, the Gulf of Mexico, and the deep southeastern Pacific at 180° from them. A second feature is that the outlines of continents form angles of about 2312° with meridians. If we examine the great continental outlines, we shall find in the circuit of the globe five eastern trends of great continents exactly 72°, or one fifth of 360°, apart. These trends mark belts of seismic force, or lines apparently where the crust has less thickness than under the median lines of continents. The rule of trends may be verified by lifting the north pole of the globe 2312° above the, wooden horizon and bringing the continental trends under the brass meridian. Professor Owen finds, third, that besides these two forces which exert their powers along lines parallel, respectively, to the axis of revolution and to that of progression, each continent has two foci nearly on its median line, concentric circles around which mark important additions to the land and orography of the continent, and pass, as they successively enlarge, through areas of consecutive geological periods from the older to the newer. One of the foci, and the dominant one in the northern continents, is near the Arctic Circle; the other is in the geographical center of the continent. The southern continents have only the latter. The foci for North America are in Boothia Felix, near longitude 96° west, and latitude 71° north, and near the height west of Lake Superior, longitude 94° west, and latitude 48° north. A radius of 24° from the northern focus reaches the southern limits of the archæan area near Lake Superior and its junction with the palæozoic; and one of 29° or 30° takes in the mesozoic of Kansas and the new red sandstone of Connecticut and Massachusetts, with a valley of erosion between. Drawing our circles from the west shore of Lake Superior, a radius of 11° or 12° gives us Silurian, lower and upper, from Niagara to near Springfield, Ohio, Lexington and Frankfort, Kentucky, and Nashville, Tennessee, dominating at least the eastern half of the circle, while the western part was still under water. A radius of 12° to 13° marks the Appalachian and other coal-fields; and of 15°, the mesozoic formation curving from the cretaceous of Utah and Colorado through the intermediate of Arkansas and Tennessee to that of New Jersey. A radius of from 18° to 24° takes in the marine tertiaries of the East and the West; one of 24° marks the main outlines of the continent; while one of 36° takes in the extreme points of the continent in all directions. The rule is applied with almost literal similarity to the other continents. Professor Owen furthermore maintains that the western Alps became a dynamic focus at about the beginning of the Cenozoic period, and that Monte Rosa is nearly the center of the dry land of the globe, whence a great circle of immense seismic activity may be traced nearly parallel with the Asiatic continental trend to the Himalayas and thence around to the Andes and the South American earthquake-region. Another great circle is nearly parallel to the North American trend, and includes the volcanoes of Central America and the geysers of Iceland, and incloses and probably aids to heat our Gulf Stream.

Value of Disinfectants.—Dr. George M. Sternberg, surgeon in the United States Army, has reported upon the results of experiments he has made with various disinfectants and vaccine virus, the conclusion drawn from which is that chlorine, nitrous acid (nitrogen dioxide), and sulphurous acid (sulphur dioxide), are reliable disinfectants in the proportion of one volume to one hundred volumes of air. Probably a considerably smaller proportion of these disinfectants would be efficient in destroying the potency of thin layers of virus in a moist state, or of virus exposed to the action of the disinfectant in an atmosphere saturated with moisture. Experiments with carbolic acid, on the other hand, "show that the popular idea, shared perhaps by some physicians, that an odor of carbolic acid in the sick-room or foul privy is evidence that the place is disinfected, is entirely fallacious, and, in fact, that the use of this agent as a volatile agent is impracticable, because of the expense of the pure acid and the enormous quantity required to produce the desired result."

A Selenium Photometer.—M. Léon Vidal has devised a photometric apparatus of selenium, for measuring the intensity of natural or artificial light by means of an action purely physical and mechanical, and in a manner analogous to that by which we measure the temperature and the amount of atmospheric pressure with the thermometer and the barometer. The difference in conductibility which results from the action of light on selenium produces deviations in the needle of the galvanometer which correspond in extent with the intensity of the luminous source. In this manner we may determine, at a glance, the intensity of light at any instant. The principle is applied to the construction of meteorological photometers, for which elements of selenium of equivalent conductibility are provided, to be substituted for each other as their molecular condition becomes modified; the plates may be restored to their normal condition by heating them, and used again. This instrument may be employed for the rapid and visible record of the instantaneous changes in luminous intensity, at all heights and depths, the observer reading the indications of the galvanometer at the place which may be most convenient for him.