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From The Saturday Review.

COMETS. *

bodies are recorded in the catalogue of comets, and the orbits of about a quarter of them THE comet which has just ceased to at- have been determined with more or less actract attention has certainly some right to curacy. Four only have been distinctly complain of the indifference of the English recognized on their re-appearance, of which public. It was scarcely, if at all, less bril- three lie within the limits of the planetary liant than that which glorified the autumn system, and the fourth, the famous comet of of 1858; and its tail was considerably more Halley, reaches but a little way beyond the elongated. Like its predecessor, it has been orbit of Neptune. Halley had the honor of pronounced a new acquisition; for no as- first predicting the re-appearance of a comet. tronomer has yet succeeded in identifying it He perceived the near approach to identity with any which has visited us before. In of the calculated orbits of the comets of spite of all these attractions, the spectacle 1682 and 1607, and on searching the past appears a sort of failure when compared with records he found another earlier appearance the exhibition of 1858. The earlier of the recorded in 1531, which satisfied him that two recent comets was honored with more his comet had a period of about seventy-five than one leader in the Times, and was made years, and ought to re-appear towards the bethe subject of innumerable communications ginning of 1759. As the time approached, to that many-sided print, of every possible the problem was treated with more exactcalibre, from the calculations of accredited ness by the French philosopher Clairaut, astronomers to the speculations of the most who fixed the middle of April as the time ignorant and conceited observers of the one when the comet would approach most nearly He claimed a margin of thirty absorbing phenomenon. This year, a lan- to the sun. guid glance at the celestial visitor through a days for error in calculation, and exactly one binocular seems to have satisfied the curi- month before the predicted time Halley's osity of average Englishmen; and the last comet was found in its perihelion position. haze of the tail has been allowed to disap- This was the comet which again appeared, pear without a single flash of nonsense on obedient to prediction, in 1835, and it is now the subject appearing in the Times. This as completely recognized a member of our contrast might be welcomed as a symptom system as any of the planets themselves. The instant that a new comet is announced, of greater sobriety of speculation having set in with the Conservative reaction, were it the first efforts of astronomers are directed not for the fact that the injudicious luminary to a comparison of its observed course with of 1861 appeared in the height of the session the records of former appearances, and some of Parliament, while its predecessor burst notion of the multitude of these bodies may upon the world in the full swing of the Silly be formed from the fact that no comet since

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Whatever the cause, it is matter for congratulation that the only literary product of this recent apparition is a republication in separate form of what is decidedly the best resume of all that is known of comets which has yet appeared. The work to which we refer is an excerpt from Arago's Popular Astronomy, and contains perhaps the best chapters of a work which attempts, with success second only to Sir John Herschel's, to popularize astronomical science. history of observed comets stretches back as far as the Chinese records of the first century. More than six hundred of these strange

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that of 1835 has been identified as an old friend. The return of some of them has

been predicted with more or less certainty from the form of their orbits, which in sevcral instances have been ascertained to be clearly elliptical while others are certain to fly off to practically, if not absolutely, infinite distances; but with the exception of the few data which have thus been arrived at,

little is known of the track of comets beyond the general fact that they move at all sorts of inclinations to the plane of the solar system, and, as often as not, in a direction opposite to that which is common to all the planets. One singular circumstance, indeed, is known of a little comet, first calculated by Encke, which revolves in a period of about three years, and has occasionally excited some alarm by its anticipated proximity to

the earth. In less than a century its period | up by the sun itself. Newton himself spechas steadily diminished by about four days ulated on the possibility of comets furnish-a fact from which astronomers have drawn ing the fuel of the central luminary, and atthe almost irresistible inference that the tributed the sudden appearance of previously planetary spaces are occupied by a rare re- unknown stars to a conflagration due to sisting medium, which must ultimately bring cometary interference. To come back to all the planets into collision with the sun. the earth, it is ascertained to be by no means This rather meagre account is all that as- improbable that the globe may gather up tronomers have to tell us about the orbits of into its atmosphere some portions of the comets, and, except in negativing a host of tails of comets which approach inconvenpopular fallacies, they have been still less iently near. Certain remarkable dry fogs, successful in the inquiry into the composi- in 1783 and 1831, were, with insufficient tion of these anomalous bodies. Popular reason, attributed to this cause; and the curiosity concerns itself more with the ques- first observation of this year's comet was tion what comets are made of than with any said to have been preceded by a peculiar investigations of their erratic orbits. To the haze, which it was sought to connect with alarmists, the little that is known on this the comet itself. But all these minor influsubject ought to be especially grateful. ences, even if more satisfactorily established, Whatever comets are made of, they seem to are insignificant matters compared with the be of a very cobwebby texture. In 1770, a possibility, so often asserted, of a conflagracomet passed outside of the moon's orbit, tion to be caused by a collision with a blazwithin the moderate distance of a million ing comet; and the first point to be settled and a half miles from ourselves. If it had is whether comets are really incandescent been as heavy as the earth it would have luminous bodies. This problem was very prolonged the year by two or three hours. happily treated by Arago himself, who deIt did not add a single second to the period monstrated that comets owe at least a large of the earth's revolution and must have been portion, if not the whole, of their light to less than a four thousandth part of the weight the reflection of the solar rays. Their light of our globe. Another comet actually thrust has the quality of reflected light; and moreitself between Jupiter and his moons without over, when they disappear, it is not in the causing the smallest appreciable disturbance way in which a luminous body becomes inof their movements. Even the most bril- visible, by gradually subtending an angle liant are transparent enough to allow stars too small to produce a sensible impression to be seen through the centre of the nucleus, of light, but by a much more sudden process and from these observations the inference caused by their increasing distance from the has been drawn that the substance of a sun, the centre of their illumination. Still comet is considerably less solid than a Lon-it is possible that some portion of a comet's don fog. Perhaps the strangest phenome-light may be its own property, and those who non ever observed was the splitting of one very familiar comet into two distinct bodies, which went on in neighboring orbits without any special symptoms of an extraordinary nature. These considerations rather tend to blunt the interest of the inquiry whether a comet is ever likely to come into collision with the earth; but Arago re-assures the timid with a calculation that the odds, in an average case, are some hundreds of millions to one against the occurrence of such an event. Still, it is not impossible; and those who delight in catastrophes which may be viewed at a distance will be rejoiced at the prediction that, after an interval of an unknown number of millions of years, several of the best known comets must be swallowed

prefer to fancy them as burning worlds may still have some shreds of argument wherewith to defend their hypothesis. But if they are not bright, comets may at any rate be hot, and every one knows the superstition about comet summers and comet vintages. Arago deals with this question as carefully as with others of more pretension. A close analysis of meteorological records shows that the average temperature of comet years has not been appreciably higher than that of others, and that extreme cold has sometimes been experienced during a comet's visit. Even the wild speculation that a comet may some day drag us by its attraction to infinitely remote regions of unwarmed space, is considered with abundant gravity;

and though it is admitted that a comet, if astronomers as much as they may have puzit were only heavy enough, and if it came near enough, might make a satellite of the earth itself, the consolation is offered that no such comet has ever been seen, and that if we were carried off to the most remote regions of space, it is by no means certain that the temperature of the earth would fall so low as to extinguish human life. The experiment would not be a pleasant one to try, and it is more comfortable to fall back on the assurance which the nebulous character of comets affords against any appreciable disturbance of our orbit.

A chapter upon tails almost completes the history of comets which Arago compiled. One thing is certain about them—they always appear denser at the edges than in the centre-a phenomenon which can only be explained by regarding them as hollow conical or cylindrical envelopes of a certain degree of transparency. But the way in which they are thrown off at the rate of millions of miles in an hour-the force which moves them the changes which they undergo the tendency to remain in general opposite to the sun, in defiance of all mechanical laws are all matters which puzzle modern

zled the earliest Chinese observers. Some would make them mere optical effects, without more substance of their own than a sunbeam shining in a darkened room. Newton made the tail a mere vapor thrown off by the heat of the sun; but neither this hypothesis nor those of Kepler and Tycho Brahé were sufficient to account for some of the most familiar facts. Biot and Gregory, Laplace and Delambre, all had theories which are discussed and rejected by Arago, whose chapter ends with a brief statement of his own solution of the problem, What is the cause of a comet's tail? The answer given is, "I do not know;" and it is the only answer which astronomers have yet been able to give to the enigma.

These are the main conclusions to be drawn from the work which has been so opportunely republished. They are not quite so ample as the hypotheses which have often been sown broadcast by less-informed writers, but they comprise all that is known on a subject which is perhaps the more fascinating from the mystery which still hangs about it.

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silver.

SUBSTITUTE FOR SILVER. - Two French | exposure to the atmosphere, or by any but the chemists, MM. De Ruolz and De Fontenay most powerful re-agents. It is without odor. have lately obtained, after several years' exper- Its specific gravity is a little less than that of iments, a new alloy, which may be very useful An alloy possessing these properties for small coin and for many industrial uses. It It can be supplied at a price forty per cent. less must be very useful to gold and silversmiths. is composed of one-third silver, twenty-five to than silver, and its greater hardness will give it thirty per cent. of nickel, and from thirty-seven a marked superiority. It may also serve as a to fifty-two per cent. of copper. The inventors substitute for gold-plated or silver-plated artipropose to call it tiers-argent, or tri-silver. Its cles, which are now so common on account of preparation is said to be a triumph of metallur- their cheapness, but which will not bear re-platgical science. The three metals, when simply ing more than a few times, and which are, in the melted together, form a compound which is not long run, sometimes more expensive than the homogeneous; and to make the compound per- pure metal. The new alloy, however, will be fect, its inventors have been compelled to use most useful for small coin. Its preparation and phosphorus and certain solvents which they have coining are so difficult that the coin made of it not yet specified. The alloy thus obtained is at cannot easily be counterfeited. Its hardness first very brittle; it cannot be hammered or would render it more durable than silver; and drawn, and lacks those properties which are es- thus the expense of re-coining, and the heavy sential in malleable metals. But after the phos- loss arising from the wearing of our silver coinphorus is eliminated, the alloy perfectly resem-age, would be greatly diminished. It is probables a simple metal, and possesses in a very high degree the qualities to which the precious metals owe their superiority. In color it resembles platinum, and is susceptible of a very high polish. It possesses extreme hardness and tenacity. It is ductile, malleable, very easily fused, emits when struck a beautiful sound, is not affected by

ble that this alloy would be more preferable for small coins than nickel-the metal which is used for the new Belgian coinage about to be issued. Apart from the objectionable color of this latter metal, there are other reasons why it would be desirable to employ an alloy similar to the one described above.

From The Athenæum.

Another Letter to a Young Physician: to which are appended some other Medical Papers. By James Jackson, M.D. Trübner & Co.

almost blind credulity may be attended with neither good nor evil consequence, but it indicates a state of popular intelligence out of which charlatans have from time immemorial made their profit. The readiness of illogical minds to reason on insufficient data, and embrace the wildest conclusions of "post hoc ergo propter hoc" reasoning, which proclaimed Joanna Stephens a public benefactor, placed Mrs. Mapp in her coach-and-four, bore

testified that painted nails and slips of wood could draw morbific virus from the human system, did not disappear together with faith in "metallic tractors." It countenanced the obscenities of Mesmer, built Graham's "Temple of Health," upheld the pernicious practices of St. John Long, and in our time furnishes Spirit-Rapping with its thousands of believers.

THOUGH Dr. Jackson's "Letter to a Young Physician" is not exactly a publication for the drawing-room table, it is one of which we should gladly hear that it had found its way into the hands of every lady in the coun-witness to the cures of Ward and Taylor, and try. Scarcely any social change is more to be desired than that women should be better instructed on the theory of medicine, and the arts and sciences pertaining to it. Led by custom and curiosity to dabble in physic, they are almost as ignorant of its first principles as were our grandmothers in the tenth degree, who centuries since doctored their children and dependants with specifics compounded of a hundred different ingredients. Natural affection and domestic convenience make them the nurses of the sick, and not unfrequently, in cases of emergency, they are the only ministrants at hand to discharge offices that would properly devolve on a regularly trained medical adviser. Yet little or no care is taken to procure them information, without which a mother will often be powerless to afford comfort to a child struggling upon her breast with needless suffering. Indeed, a proposal to instruct ladies in nosology and the mysteries of the pharmacopioa would shock the delicacy or excite the ridicule of most persons able to bring about a better state of things. The result of this unwise treatment of an important subject is, that, as a rule, gentlewomen regard a physician's prescription with the same sort of superstition as was formerly expended on amulets and charms, and in pure simplicity believe a dose of medicine to be a mysterious agent capable of driving disease out of the body. If Dr. Allopath's pills are taken previous to the abatement of a fever, to Dr. Allopath's pills the improvement is attributed; if Dr. Homœopath's globule is administered an hour before the advent of a refreshing sleep, Dr. Homœopath's globule gets all the credit of the change for the better; and just as the chamber in which a patient recovers under the kindly efforts of nature has been presided over by Dr. Allopathor Dr. Homoeopath, so the one or the other is held by the spectators to be a "wise man." In a particular case this

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The time, we trust, is not far distant when a writer of competent attainments and impartial judgment will offer the public a satisfactory history of medicine,-not a compilation wandering over thrice ten centuries of scientific darkness, with a show of erudition filched from Le Clerc and Freind; but a sound, honest history of medicine during the last hundred years, referring to the ancient schools only to display the causes of their errors, and having for its chief object the exposition of those facts and principles which, even at the present unsatisfactory stage of medical science, recent investigations have conclusively ascertained. Until public intelligence is better informed both as to what is really known, and as to the means by which we may reasonably hope to attain further knowledge on subjects concerning which no one can be indifferent, ignorant pretenders, be they ambitious knaves or mere self-deluded enthusiasts, will find a submissive crowd of worshippers and victims. In the mean time it is something to have a physician of reputation come forward and frankly avow how far, and under what circumstances, medical science can cope with disease. It is well for the invalid of average education and sagacity to know that one of the most enlightened physicians of the present century admits that all he can effect in the practice of his profession is, in certain cases-such cases being by no means a majority of those that seek his treatment-to assist nature in working her own cure :—

that she needs. Just so, the physician, in the larger number of cases under his care, makes it his business to dispose of every thing relating to his patients in such a manner as to give the best chance for the salu

"When a surgeon is called to a man with a broken leg [writes Dr. Jackson], he places the limb of his patient, and in some measure his whole body, in a fixed position, using splints and bandages; and then he watches him from day to day. He does not pretend tary operation of the natural powers. A that the processes of healing in the fractured bone are brought into operation by the splints and bandages, nor by his watching. But he has placed the injured parts under the circumstances most favorable for healing; and he watches that he may guard against every thing which can interfere with the salutary operations of nature, as well as that he may give to her any support which he may think

good nurse, it may be said, may do the same. But the qualifications of a well-educated physician must enable him to take the case with much greater advantage."

Testy innovators, who are fond of railing at the intolerance of Orthodox Medicine, will do well to take a lesson of moderation from an orthodox physician.

BOTTOM OF THE OCEAN.-Mr. Green, the ▾ famous diver, tells singular stories of his adventures, when making search in the deep waters of the ocean. He gives some sketches of what he saw on the Silver Banks, near Hayti:—

"The banks of coral on which my divings were made, are about forty miles in length, and from ten to twenty in breadth.

"On this bank of coral is presented to the diver one of the most beautiful and sublime scenes the eye ever beheld. The water varies from ten to one hundred feet in depth, and is so clear, that the diver can see from two to three hundred feet, when submerged, with little obstruction to the sight.

"The bottom of the ocean, in many places on these banks, is as smooth as a marble floor; in others it is studded with coral columns, from ten to one hundred feet in height, and from one to eighty feet in diameter. The tops of those more lofty support a myriad of pyramidal pendants, each forming a myriad more; giving the reality to the imaginary abode of some water nymph. In other places the pendants form arch after arch, and as the diver stands on the bottom of the ocean, and gazes through these into the deep winding avenue, he feels that they fill him with as sacred an awe as if he were in some old cathedral, which had long been buried beneath 'old ocean's wave.' Here and there, the coral extends even to the surface of the water, as if those loftier columns were towers belonging to those stately temples now in ruins.

"There were countless varieties of diminutive trees, shrubs, and plants, in every crevice of the corals where the water had deposited the least earth. They were all of a faint hue, owing to the pale light they received, although of every shade, and entirely different from plants I am familiar with, that vegetate upon dry land. One in particular attracted my attention; it resembled a sea-fan of immense size, of variegated colors, and of the most brilliant hue.

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like sunfish; from those of the dullest hue, to the changeable dolphin; from the spots of the leopard to the hues of the sunbeam; from the harmless minnow to the voracious shark. Some had heads like squirrels, others like cats and dogs; one of small size resembled a bull terrier. Some darted through the water like meteors, while others could scarcely be seen to move.

"To enumerate and explain all the various kinds of fish I beheld while diving on these banks, would, were I enough of a naturalist so to do, require more space than my limits will allow, for I am convinced that most of the kinds of fish which inhabit the tropical seas can be found there. The sun-fish, saw-fish, star-fish, white shark, ground shark, blue or There shovel-nose sharks, were often seen. were also fish which resembled plants, and remained as fixed in their position as a shrub. The only power they possessed was to open and shut when in danger. Some of them resembled the rose in full bloom, and were of all hues. There were ribbon fish, from four to five inches to three feet in length. Their eyes are very large, and protrude like those of the frog. Another fish was spotted like the leopard, from three to ten feet long. They build their houses like the beaver, in which they spawn, and the male or female watches the ova till it hatches. I saw many specimens of the green turtle, some five feet long, which I should think would weigh from four to five hundred pounds."

DURING the siege of Sevastopol, a Russian shell buried itself in the side of a hill without the city, and opened a spring. A little fountain bubbled forth where the cannon-shot had fallen, and during the remainder of the siege afforded to the thirsty troops who were stationed in that vicinity an abundant supply of pure cold water. Thus the missile of death from an enemy, under the direction of an overruling Providence, proved an almoner of life to the parched and weary

"The fish which inhabited those silver banks, I found as different in kind, as the scenery was varied. They were of all forms, colors, and sizes from the symmetrical goby, to the globe-soldier of the Allies.

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