Popular Science Monthly/Volume 5/August 1874/Miscellany
The Priestley Celebration at Northumberland.—The proposition for a Chemical Centennial, alluded to in the June number of the Monthly, has taken practical shape, and is to be carried out by a meeting or celebration at Northumberland, Pa., beginning on the 31st of July, 1874. A large number of the eminent chemists of the country have united in an invitation to their brethren to participate in the exercises of the occasion, in the belief that it will foster a feeling of fraternity, and afford a fitting opportunity for that interchange of ideas so important to the advancement of science. Prof. H. Carrington Bolton, of the Columbia College School of Mines, is chairman of the general committee having the matter in charge, and any information respecting the arrangements for the meeting may be obtained by addressing him. In a circular issued by this committee, those planning to attend the meeting at Northumberland are requested to send their names to Dr. Robert McCay, of that place, secretary of the local committee of which Dr. Joseph Priestley is chairman.
In order to add to the interest of the occasion, a Loan-Exhibition will take place during the meeting, for displaying apparatus, books, manuscripts, etc., etc., belonging to Dr. Priestley, or other objects illustrating the history of chemistry. Gentlemen interested are earnestly requested to contribute any thing in their possession appropriate to this exhibition. It is expected that the exercises will include an address by Prof. Joseph Henry; a sketch of the life and labors of Priestley, by Prof. Henry H. Croft; a review of the century's progress in theoretical chemistry, by Prof. T. Sterry Hunt; a review of the century's progress in industrial chemistry, by Prof. J. Lawrence Smith; and an essay on American contributions to chemistry, by Prof. Benjamin Silliman. Detailed programmes of the exercises will be distributed at the meeting.
Belt's Theory of Cyclones.—In the "Naturalist in Nicaragua," Mr. Belt has the following on the origin of whirlwinds and cyclones: "I am confident that a study of the smaller eddies of air is the proper way to approach the difficult question of the origin of cyclones." The movements of these small whirling masses may be observed from the outside, and their progress traced from the incipient stage to that of dissolution. In the beginning of a whirlwind there is a movement near the surface of the ground of light particles of dust toward a centre, attended or occasioned by a rotary motion of the air. This quickly rises into a whirling column from fifty to a hundred feet or more in height. On the dry hot plains of Central and South America, and of Australia, this phenomenon is of frequent occurrence, and is not unusual in our temperate latitudes in summer. The whirling columns, according to Mr. Belt, differ in diameter from a few feet to many miles, and his opinion is that "there is a complete gradation from the little dust-eddies, through larger whirlwinds and tornadoes, to the awful typhoons and cyclones of China and the West Indies."
In the small whirlwinds which occur over the land, there is no evidence of the condensation of vapor occurring in dry air. But, where the atmosphere is charged with humidity, as over tropical seas, the condensation is great. The notion, therefore, that whirlwinds and tornadoes originate in sudden condensation, Mr. Belt thinks not well founded, the phenomenon being an incident rather than a cause of the movement. Nor is the theory a satisfactory one, that the meeting of conflicting currents of air and consequent condensation give rise to the phenomenon. Attention is directed to the fact that many terrible whirlwinds are dry, and ran their course without producing rain or cloud. They originate at or very near the surface of the ground, where the air becomes intensely heated. "The quivering of the air over hot ground foreshadows the whirlwind as mirage does the simoom, and sultry heat and oppressive calm do the hurricane." In the stratum of heated air next the ground resides the energy which produces the whirlwind. That this, in many instances, is prevented from rising, has been proved by numerous observations. At last the upward tendency becomes so strong that it breaks through the overlying heavier air, and there occurs an upward discharge, followed by all the phenomena of whirlwinds.
Dupuy on the Functions of the Brain.—Dr. Eugène Dupuy, of Paris, has repeated Ferrier's experiments on the brain, with results which do not accord with those of the English physiologist. In the Monthly for December last we gave an account of Ferrier's researches, and hence it will suffice to say here that in his experiments stimulation of the superior external convolution of the brain produced movement of the animal's paw; of the mid-frontal region, contraction of the eyelid; of the parietal region, movement of the ear; of the lower frontal and orbital regions, movement of the tongue. He therefore concludes that in these regions there are actual centres for the movements obtained. Dupuy, on the other hand, wherever the electrodes were placed, whether on the frontal, parietal, or orbital convolutions, succeeded only in obtaining, on slight stimulation, movements of the opposite fore-paw, which, on stronger stimulation, extended to the whole of that side of the body. Further, the electrodes applied to the uninjured surface of the dura mater over the convolutions produced the same effect as when placed on the exposed convolutions themselves.
Dupuy was led to suspect that the electrical stimulation might in these cases be so diffused through the whole hemisphere as to affect directly the base of the brain or even the nerves arising there. To ascertain the truth of this matter he laid bare one-half of the brain of a dog, under complete anæsthesia, and applied to the posterior extremity of the hemisphere the nerve of a galvanoscopic frog, duly insulated. The electrodes were then placed on the front of the hemisphere, and movements produced in the opposite fore-paw, the legs of the frog being simultaneously thrown into violent contraction. Upon another dog, under partial anæsthesia, he divided the corpus striatum and optic thalamus on one side, the corpus callosum having previously been cut through. The electrodes were then placed on the convolutions above and behind the Sylvian fissure. With a strong current, not only the fore-leg of the opposite side, but also the hind-leg, exhibited contraction. In another experiment he removed the whole cerebral mass above the pons Varolii, and applied the electrodes to the cut surface; muscular contractions resulted, limited to the fore-limbs, right and left. These results, many times obtained, render it certain, according to Dr. Dupuy, that electrical stimulation, to whatever part of the brain it may be applied, is widely diffused; and that such diffused stimulation, reaching the base, and there affecting the nuclei, the medulla, or the nerves themselves, will explain all the phenomena obtained by Ferrier and by himself on faradizing the convolutions.
The Sponge-Fisheries.—The chief industry of the Sporades Islands, in the Grecian Archipelago, is the sponge-fishery. The yearly average crop of sponges is estimated at £120,000 sterling. The diving-apparatuses used in the fishery are imported exclusively from England and France. Though there is no difference in construction between English and French machines, with regard to the depth they can attain, or the length of time a diver can remain under water, still English apparatus generally proves stronger, and the gears are of superior quality. The air-tubes, however, have hitherto labored under the disadvantage of being heavier than the French, thus impeding the free movements of the diver, the tubes being caught among the rocks. But, samples of French floating tubes having been sent to England, the result has already been a great improvement in the manufacture of the English article. A common fraud practised by traders in rough sponges is to introduce into them a quantity of sand, so as to add to their weight. In order to guard against this, agents are now sent to Rhodes, which is the centre of this commerce, to purchase the sponge from the divers or owners of diving-apparatus. In this way the article may be got at first hand, without being weighted with
Alligators swallowing their Young.—Colonel Caleb G. Forshey, of the New Orleans Academy of Science, à propos of the question whether snakes swallow their young, states that this habit is certainly found among alligators. "That alligators swallow their young," says Prof. Forshey, "I have had ocular demonstration in a single case; and have the universal tradition of negroes and whites in this region of Louisiana, Mississippi, and Texas, that such is their habit. In the winter of 1843-'44, I was engaged making a survey on the banks of the Homochitto Lake. The day was warm and sunny, and, as I halted near the margin of a pond partly dried up, to pick up some shells, I started a litter of young alligators, that scampered off, yelping like puppies, and retreating some twenty yards to the bank of Lake Homochitto. I saw them reach their refuge in the mouth of a five-foot alligator. She evidently held open her mouth to receive them, as, in single file, they passed in beyond my observation. The dam then turned slowly round, and slid down beneath the water, passing into a large opening in the bank, beneath the root of an ash-tree. Doubtless this refuge is temporary, and the young are released at their own or the mother's pleasure."
Le Conte on the Origin of Western Mounds.—Prof. Joseph Le Conte, in the American Journal of Science, discusses the origin of the mounds with which the prairies near Puget Sound are studded, and from which they get the name of "mound prairies." These mounds are generally three or four feet high, and thirty to forty feet in diameter at the base. There are millions of them, and they stand so thickly as to touch each other at their bases, leaving no level space between. They consist wholly of a drift-soil of earth, gravel, and small pebbles, the intervals being thickly strewed with larger pebbles and small bowlders. The vegetation of the mounds is mostly ferns; the intervals are covered with fine grass only. Some have supposed that they are Indian burial-mounds; others have thought that they are artificial mounds, upon which were built huts of Indian villages. They have also been supposed to be large fish-nests, dating from the period when these prairies were the bottoms of shallow inlets of the sea. The author holds them to be the result of surface-erosion under peculiar conditions. In another part of the State, viz., between the Dalles and the upper bridge of the Des Chutes River, a distance of about thirty miles, the whole country is literally covered with mounds of this kind. Here they vary in size, from scarcely detectible elevations, to mounds five feet high and forty in diameter at the base; and in form from circular, through elliptic and long elliptic, to ordinary hill-side erosion-furrows and ridges. In regularity of size and position there is equal diversity; in some places being as complete as at Mound Prairie, while, in other places, they are of different sizes, and often separated by wide, pebble-covered spaces, as if they were but the remnants of a general erosion of the surface-soil. No one, says Prof. Le Conte, can ride over those thirty miles, and observe closely, without being convinced that these mounds are wholly the result of surface-erosion, acting under peculiar conditions. These conditions are, a treeless country, and a drift-soil, consisting of two layers—a finer and more movable one above, and a coarser and less movable one below. Surface-erosion cuts through the finer superficial layer, into the pebble-layer beneath, leaving, however, portions of the superficial layer as mounds. The size of the mounds depends on the thickness of the superficial layer; their shape depends much on the slope of the surface. The process once started, small shrubs and weeds take possession of the mounds, as the better soil, and hold them by their roots, and thus increase their size, by preventing or retarding erosion. The treelessness of Eastern Oregon has been produced gradually, since post-tertiary times, by the increasing dryness of the climate. We may imagine the mounds, therefore, as having been held by the struggling remnants of a departing vegetation. At Mound Prairie, however, the treelessness is probably produced by a contrary condition, viz., the extreme wetness of these lower level spots in winter. Here, therefore, the weeds and ferns hold and preserve the mounds, not only as the better soil, but also as the drier spots.
The Value of Vivisections.—Prof. M. Schiff, of Florence, whose vivisections gave rise to the recent controversy on the cruelty of the practice, has published a book, in which he states the results of his experiments. The following quotations from this work will best show whether, as the opponents of vivisection have claimed, experiments of this kind "lead to no useful result," or are to be classed as "acts of needless cruelty." Prof. Schiff has studied the comparative effects of ether and chloroform on the animal economy. Ether, according to him, is preferable to chloroform as an anæsthetic, because etherization, even when pushed to the very last stage of insensibility, is never dangerous to life, so long as one maintains the act of respiration. And even if one presses the inhalation of ether still further, so that the respiratory movements cease, life is never menaced, if, at the moment of the paralysis of the thoracic walls, artificial respiration is immediately commenced. Chloroform has been preferred to ether because it acts more quickly, and its use is more agreeable to some persons. But chloroform has a paralyzing action much greater than that of ether, and, in like manner, has a special influence on the nerves of the heart, and of the vessels. If the inhalation of chloroform is carried so far as to produce a considerable weakening of the respiratory movements, the interruption of the inhalation may, in a majority of cases, lead to the reëstablishment of respiration, and, afterward, of sensation; but sometimes, in a few moments after the commencement of inhalation, the force of the circulation is so enfeebled that the blood passes sluggishly through the lungs, and its rate of renewal or revivification is much diminished. The blood in the body no longer comes into necessary contact with the atmospheric air introduced by respiration into the lungs. If the action of chloroform is prolonged until respiration ceases, we are not even sure of being able to revive the person, after having reëstablished the respiratory movements; for these often again cease, owing to the disturbance of the circulation, while these same movements, if restored after the inhalation of ether, become always more frequent in the patient when left to himself. Prof. Schiff affirms that, in the present state of science, the medical man is responsible for every case of death occasioned by the application of ether, because a careful watching of the respiration is capable of preventing death, while the fatal effect of chloroform depends, in part, on individual predisposition, which the physician is unable to recognize.
Animals and Fire-arms.—That crows and many other species of birds have little fear of man when he is unarmed is a familiar fact, and suggests that they fear him chiefly because of the weapons he carries. In Scotland, where shooting was prohibited on Sunday, crows and rooks were gentle, and fed around buildings without concern. Singularly enough, the same thing was observed of animals by Dr. Tristram when traveling in the wilderness of Moab, where the sound of a gun is quite rare. He says: "We were struck with the sagacity which all the wild animals showed in the matter of fire-arms, little familiar as they can be with them here. As it was Sunday, we strolled or sat down among the ruins without our fowling-pieces, and were consequently objects of indifference. A fine fox sat and looked at us a dozen times among the stone-heaps, and just walked away, keeping almost within gunshot all the afternoon. The Sakkr falcon sat calmly on his favorite perch, and allowed us to reconnoitre him on Sunday, while the eagle, owls, sand-grouse, and partridge, showed a similar contempt for unarmed Europeans."
The Temperature of the Ocean.—Dr. Carpenter recently delivered a lecture before the London Royal Institution, on the "Temperature of the Ocean," showing, from the soundings made by the Challenger Expedition, that the difference of climate between Northwestern Europe and the North American Atlantic seaboard is due not to the course of the Gulf Stream, but to the circulation of the waters of the Ocean between the poles and the equator. The shores of Northwestern Europe have the benefit of the northward movement of the warm superficial stratum, while the temperature of the American coast is lowered by the surging up against it of deep glacial underflow. The fact, he says, comes out most clearly from the Challenger soundings, which had been suspected by the United States Coast Surveyors, that the cold band which separates the Gulf Stream from the United States coast is really continuous with the cold strata that lie at some depth beneath the Gulf Stream, and this continuity explains the presence of the cold band which was previously wanting. For, as any flow of water from the equator toward either pole will tend toward the east in virtue of the excess of easterly momentum it brings from a part of the globe where its rotation was rapid; so any flow of water proceeding from either pole toward the equator will tend toward the west, in virtue of that deficiency of easterly momentum which it derives from a part of the globe where its rotation was less rapid. In this surging upward of the deeper and colder stratum lying beneath the Gulf Stream, we have very distinct evidence of its southerly movement. The precisely similar cold band which has been observed by Captain St. John to separate the Kuro Liwo, or warm Japan current, from the coast, may be fairly attributed to the same cause.
Action of Frost on the Position of Trees.—The elevation of the trunks of trees was the subject of some observations by Mr. Thomas Mechan at a recent meeting of the Philadelphia Academy of Sciences. On a previous occasion he had attributed this elevation to the natural thickening of the roots, which brought them in contact with unyielding rock beneath, the necessary consequence being that they would then lift the entire tree. Since that time he has been led to offer another explanation, viz., the action of frost. Most trees standing by themselves, he observed, have the collar of much greater diameter than the trunk above, and the upper portions of the roots, springing from about the collar, are considerably above the surface of the ground. That this is caused by the action of frost is rendered probable by what we know of its action on minor vegetation, what is called "drawing out." When the land freezes, expansion ensues, drawing up with it the roots of clover, and leaving of course a cavity from which the root was drawn. At the first thaw the liquid, carrying earthy matter, enters the cavity, and then the clover-root is prevented from descending to its original position. The same is true of trees. Roots, heaved up by frost, find the cavity beneath partially filled, and hence the tree will stand a little higher than before. Dr. Latham, State Botanist of Wisconsin, is of the opinion that large trees blow over much more readily than younger ones with the same, proportional weight of head to development of roots, chiefly because the older trees have been drawn nearer to the surface. One of the chief offices of the tap-roots is probably to prevent the tree being lifted too high by the frost. Dr. Mechan is inclined to think that the trees of tropical climates have by no means so great a development of taproots as those of more northern regions. This question he proposes to investigate further.
Topography of the Bed of the Pacific.—Soundings made by the United States Steamer Tuscarora, between San Diego, Cal., and Honolulu, S. I., show this part of the Pacific to be a basin with precipitous sides and a comparatively level bottom. In the first 100 miles west from San Diego, there appear to be two valleys and two peaks. The first valley is from 622 to 784 fathoms deep, the first peak 445 fathoms, the second valley 955 fathoms, and the second peak 566 fathoms. Thence a precipitous fall takes place, giving, in latitude 31° 43' north, longitude 119° 28' west (Greenwich), 115 miles from San Diego, a depth of 1,915 fathoms. After that there is a gentle slope, with comparatively unimportant interruptions, at the rate of three feet to the mile, to the point of greatest depth, 3,054 fathoms, at a distance of about 400 miles east of Honolulu. The sharpest elevation is a rise about midway between the United States and the Sandwich Islands, in latitude 26° 30' north, longitude 127° 37' west, the highest portion of which is 2,159 fathoms below the surface. At the next cast of the lead the valley to the west of this elevation took 2,650 fathoms. The fall of the side of the basin, east of Honolulu, is even more remarkable than the descent off the American coast. Fifty miles from Honolulu soundings gave 498 fathoms; 40 miles farther east, in latitude 21° 43' north, longitude 156° 21' west, the depth was 3,023 fathoms. Between the last-mentioned point and that of greatest depth a hill rises, on whose summit there are only 2,488 fathoms of water.
The Origin of Hair-Snakes.—Dr. Slack, in the Turf, Field, and Farm, satisfactorily answers the question put by a correspondent, as to the origin of the so-called hair-snake or hair-worm. The common belief is that these creatures are a transformation of a horse-hair that has remained for some time in water. "When a walking-stick," says Dr. Slack, "becomes a snake, a horse-hair will become a worm. As the former miracle has not taken place since the departure of the Israelites from Egypt, it is safe to conclude that the latter transformation has not recently been made. A dry hair placed in water will absorb the moisture, and, from the unequal expansion of the exterior and interior layers, will become contorted; so too, would a piece of two-inch rope, yet we have never heard of the latter having been accused of possessing vitality. The hair-snake is a living creature, endowed with organs of locomotion and respiration, and capable of propagating its species. Scientifically it is known as Gordius aquaticus, the generic name being derived from the Gordian knot, in allusion to the tangled appearance often presented by a multitude of these animals. The specific name aquaticus is not so appropriate, for they thrive out of water." Dr. Slack has taken Gordii six inches in length from the body of a grasshopper. They have also been found in the stomachs of insectivorous birds.
Cast and Wrought Iron Stoves.—A commission of the French Academy of Sciences has been investigating the hygienic effects of the use of cast-iron stoves. Experiments were made with stoves of wrought and cast iron, using soft coal, with the view of learning under what conditions stoves of metal became unhealthy, through the presence of carbonic acid and carbonic oxide, in the rooms heated by them. Rabbits were made to breathe the air passing over stoves of cast and wrought iron heated to redness, and afterward the blood of the animals was chemically examined, to ascertain the presence of carbonic oxide. The report states that, though the results of experiments made upon rabbits do not enable us to fix with precision the proportion of carbonic oxide absorbed by their blood, nor that of the oxygen which has been expelled from it, still they show that the use of cast-iron stoves, at a red heat, causes in the blood, by the presence of carbonic oxide, a gas eminently poisonous, changes whose repetition may become dangerous; while the same method of investigation has not revealed analogous effects from stoves of wrought-iron. In summing up the results of the entire series of experiments the commission reports as follows:
"The carbonic oxide, whose presence has been proved when stoves of cast iron are used, may arise from several different causes: 1. The permeability of the stove by that gas, which will pass from the interior of the fire-pot to the exterior. 2. The direct action of the oxygen of the air upon the carbon of the cast-iron heated to redness. 3. The decomposition of carbonic acid contained in the air by its contact with metal heated to redness. 4. The influence of the organic dust naturally contained in the air." The commission recommend that all stoves and heating apparatus of cast-iron, and even of wrought-iron, be lined with fire-brick, or other substance, so as to prevent their attaining a red heat.
South-Sea Surgery.—In some of the South-Sea Islands a method of surgical treatment is adopted in certain cases which would bear away the palm, as a torturing process, even from the dreaded moxa. The following description of the South-Sea operation is from the London Medical Times: "The wise men in these islands have invented a theory that headache, neuralgia, vertigo, and other affections of the head, arise from a crack in the skull, or from pressure of the skull upon the brain. The remedy which they have contrived consists in laying open the scalp by a T-shaped incision, and then gently scraping away the cranium itself with a piece of glass until the dura mater is reached, and a hole is made in the skull as large as a silver dollar. Of course, if the operation is carried a little too far, the patient dies; and this appears to be the mode in which most of the cures are effected, death being the result in about half the cases operated upon. The hole is usually covered with a piece of cocoa-nut shell, scraped thin, and placed under the scalp. Formerly, the instrument employed was a shark's tooth, but broken glass is found to act better. Bone-scraping is also resorted to as a cure for rheumatism in old people. The skin is cut open, so as to lay bare the bone supposed to be affected, and the surface of the latter is then scraped until a portion of the external lamina is removed. Here surely the remedy is worse than the disease."
New French Life-saving Raft.—An extraordinary safety-raft has recently been invented in France. It is described as large enough to support from 400 to 600 persons, as neither incumbering nor requiring any alteration in the arrangement of vessels, and as needing only a minute or two to inflate and launch it. It is an airtight mattress, with a surface of nearly 900 square feet, inflated in one minute, it is said, from a reservoir fixed in the engine-room, and always charged with air under a pressure of fifteen atmospheres. When not in use it is rolled up, and takes no more room than a boat. When inflated it falls over the side of the vessel, against which it is retained by ropes till all the persons on board are transferred to the raft. Three strong spars, passing through the whole length of the raft, keep it flat and solid.
Training Shepherd-dogs.—Sheep-raisers in California have an ingenious system for training dogs to guard their flocks. In Southern California one may wander for miles, and see thousands of sheep without a single shepherd to watch them, but around each flock half a dozen dogs. These have the entire care of the sheep, drive them out to pasture in the morning, keep them from straying during the day, and bring them home at night. These animals have inherited a talent for keeping sheep, and this talent is cultivated in the following way: When a lamb is born, or the shepherds have a pup which they want to train, the lamb is taken from its mother, she not being allowed to see her offspring, and the puppy is put in its place, and the sheep suckles it. When the puppy grows old enough to eat meat, it is fed in the morning and sent out with the sheep. It stays with them, because it is accustomed to be with its foster-mother; but it cannot feed with them, and, as they get full, the dog grows hungry. At length, impatient to return, in hopes to get its meat, the dog begins to tease and worry the mother, and finally starts her toward home; the others follow, and thus the whole flock is brought in. If they are brought home too early, or the dog comes without them, he gets punished in some way; and thus, by taking advantage of their instincts and appetite, these dogs are trained to a great state of perfectness, and become invaluable to the owners of large flocks.
Legislative Blunders.—The Pall Mall Gazette thus indicts the English Public Health Act of 1872: "Its failure, now that this has become too clear to be diluted, turns out to be of a more than usually instructive kind; for it shows that, contrary to all expectation and probability, there was, in 1872, still a blunder remaining for us to commit in sanitary administration, and that we have since committed it. We had already exhausted every source of administrative inefficiency which is to be found in inadequacy of powers, defects of initiative, and obscure intricacy of law. We had set up sanitary authorities who could not act, authorities who would not act, and authorities who did not know when, where, and how to act: it remained for us to establish authorities who could and must act, and then to misdirect and mislead them into a confusion worse than inactivity. Having failed in every possible way at the circumference, we had yet to fail at the centre, and we have done it."
Skunk-Madness.—Rev. Horace C. Hovey, in the American Journal of Science, gives some novel results of a protracted inquiry concerning the common skunk (Mephiitis mephitica). He says that, at times when the animal is unable, either from exhaustion or other reasons, to produce that secretion whose stench is its great defense, its bite is productive of a highly-dangerous rabies, often causing death with some of the terrible symptoms of hydrophobia. We have thus authenticated the fact that rabies, capable of being given by the inoculation of a bite, is communicable by the canines, felines, and the mustelidæ families.
How Plants imbibe Ammonia.—From a series of experiments made by Adolf Mayer, it appears that plants have the power of absorbing ammonia through their aërial parts. The experiments were made on plants growing in such a manner that no ammonia could reach their roots directly, while the leaves were subject to its action, in either a gaseous or dissolved condition. It was observed, however, that the plants did not thrive when the access of ammonia to the roots was entirely prevented.
Reproduction of Organs in Fish.—Darwin, in his "Animals and Plants under Domestication," states, on the authority of Frank Buckland, that, when portions of the pectoral and tail-fins of various fresh-water fish are cut off, they are perfectly reproduced in about six weeks. This phenomenon of regeneration was recently observed in the aquarium of the Boston Young Men's Christian Union, by F. W. Clark, who communicates to the American Naturalist an interesting note on the subject. It appears that, in the spring of 1873, a fish-fungus made its appearance in the tank, and several fine fishes died. Among the specimens attacked by the fungus was a young goldfish, which, by some unknown means, had lost its tail-fin. The fungus covered the whole stump of the tail; the fish became sick, and was apparently dying. Mr. Clark's attention having been called to the case, he at once concluded that he had some parasite to deal with, and resolved to exterminate it. He applied a few drops of nitric acid to the tail-stump, allowing it to remain a moment or two, after which he rinsed it off in clean water, and put the fish back in the tank. The parasite, of course, was killed; the patches of fungus sloughed off, and the fish was soon well. In the course of a few days. he thought he saw the fungus again appearing on the affected part; but, on looking closely, found that the appearance was really due to the growth of new rays. A month later, a new tail-fin, about a fourth of an inch long, had appeared, and, three months from the time of the experiment, the fish was undistinguishable from others of the same species in the aquarium.