finger, A breeze sighs through the rushes dried and sere, And autumn clouds hang their dank tresses over The Nymph of Summer on her lonely Longman's Magazine. THE SPRING-TIDE COMES. She scatters daisies o'er the hills; That crown her head on fell and brae. spray; Bright is the marsh-flower's golden ray, The young lambs round her footsteps play; The tassels on the larches sway; The blackbird's song the valley fills; The Spring-tide comes. Chambers' Journal. MAGDALEN ROCK. SONNET. FOR her gait if she be walking, And shrinks before him as the blossoms Be she sitting I desire her o'ercome her, For her state's sake, and admire her Gait and state and wit approve her; Be she sullen, I commend her Hears, through the silence of the autumn For a modest; be she merry days, The sad-voiced robins singing out the sum- Briefly, everything doth lend her mer And dead leaves falling thick in wood land ways. So much grace and so approve her, WILLIAM BROWNE. of air to a certain degree, it passes directly into vapor. On a planet, in fact, possessing an atmosphere hundred and sixty-five times rarer than our own, liquid water could not exist. one From The Edinburgh Review. observation. No criterion was, howTHE LIQUEFACTION OF GASES.1 ever, at hand by which to decide THE "third state" of matter was whether, in so doing, it constituted an formally recognized by Van Helmont, exception or followed a rule. Indeed, a Belgian alchemist, early in the seven- we are still ignorant of any abstract teenth century. But his discovery principle bearing on the subject. might have slipped back into oblivion Thus, apart from actual experience, had he not emphasized it by the inven- there could be no well-grounded assurtion of a name. The unseen and un-ance that the behavior of water would felt, yet material, substances brought prove typical. Under altered condiinto notice by his researches were tions it even departs from its own called by him "gases," and are called standard. In a partial vacuum ice so still. Atmospheric air was not in- cannot be melted. When heated above cluded among them. For it ranked in freezing-point, in a vessel exhausted those days as an "element" in the Aristotelian sense. Boyle, however, became aware of its composite character, though he failed to isolate the "vital" ingredient, the existence and functions of which he divined. It was Whether placed as near to the sun as not, indeed, until more than a century later that oxygen was definitively captured by Priestley and Scheele. Carbonic acid, meanwhile, had been investigated by Black; Cavendish condensations would invariably take gave, in 1766, the earliest description of "inflammable air," alias hydrogen; and nitrogen was made known by Priestley in 1772. Then Lavoisier, extricating these valuable discoveries tion of heat very quickly tears their from the misapprehensions in which they lay involved, and bringing them into logical connection with the results of his own inquiries, shaped the new science of pneumatic chemistry. Matter in general was thenceforward systematically studied under its solid, liquid, and gaseous forms. But there was as yet no certainty that every individual kind of matter was capable of assuming each in turn. One example of this versatility had, it is true, been at all times familiar. Water undergoes its cycle of changes from ice to steam naturally, and as a matter of common 11. The Chemical Work of Faraday in relation to Modern Science. Lecture delivered at the Royal Institution, June 26, 1891. By Professor 2. Magnetic Properties of Liquid Oxygen. Lecture delivered at the Royal Institution, June 2, 1892. By Professor Dewar, M.A., F.R.S. 3. Liquid Atmospheric Air. Lecture delivered at the Royal Institution, January 20, 1893. By Professor Dewar, M.A. F.R.S. Lecture 4. The Scientific Uses of Liquid Air. delivered at the Royal Institution, January 19, 1891. By Professor Dewar, M.A., F.R.S. Mercury, or as far from him as Neptune, such a globe could show neither seas nor streams. No rain could fall there, no dew be deposited; aqueous the form of snow. Sublunary experience, too, makes us acquainted with many complex substances which cannot change their state, because the applica innermost structure to pieces. Who, for instance, would attempt to melt wood or leather? The very idea seems absurd, because every one knows that they char or burn while still solid. That is to say, they cease to be, as wood or leather, long before their respective ideal fusing-points are reached. Elementary bodies cannot, of course, be decomposed; but some resist liquefaction, if not absolutely, yet at least so far as to sublime without melting, like ice in a vacuum. One of these is arsenic. And carbon volatilizes only at an enormously high temperature, and has never been liquefied. Possibly the intermediate state might be forced upon it by accompanying great heat with high pressure; but the idiosyncracies of chemically distinct substances are so peculiar that its reluctance may represent real inability to liquefy. The law, however, of the three states of matter is most probably universally nothing but oxygen chemically condensed, possesses highly characteristic qualities of its own. valid both for simple bodies and for influences of heat, light, electricity, or stable compounds. The power by chemical affinity; but the operation is which it is enforced resides in heat. destructive of the body originally comNear the bottom of the scale of tem-posed by them, and the new ones by perature, solidification reigns supreme; which it is replaced are often wholly towards the opposite extreme, vapor- diverse from it in their qualities and ization. The moon exemplifies the relationships. Thus, each of the ultifirst condition, the sun the second. mate particles of water consists of at Between the two stands our earth, in least three unimaginably minute porwhich solids, liquids, and gases co- tions-two of hydrogen and one of exist. It is composed, in other words, oxygen-the separation of which inof the three antique " elements," volves the demolition of water and the earth, water, and air. Now, the fact substitution for it of its gaseous conthat, under the same circumstances, stituents. Conversely, oxygen is condifferent substances are differently ag- verted into ozone when its molecules gregated is none the less remarkable are compelled, through the action of for being tritely familiar. It seems a electricity, to annex each a third atom matter of course that our atmosphere of the stuff itself. Yet ozone, though should, at all times and seasons, remain imperturbably ethereal that that rigid rocks should enclose a heaving ocean, and that mercury, alone among metals, Molecular structure, then, and the should flow like water. And it is easy forces of which the modes of action are to see that the prevalence of such like modified by it, determine the properincongruities is essential to the scheme ties of matter. A molecule is a subof things to which we ourselves belong. microscopic piece of mechanism Unanimity among the various kinds of exquisite flexibility, conjoined, in many matter in freezing, melting, and boil-cases, with a high degree of stability. ing, would obviously exclude the possi- An organic whole, complete in itself, it bility of life. The question, then, why is nevertheless sensitive to manifold it is excluded, answers itself; but if influences from without. It is all alive we go on to ask how it is excluded, we with energy in the shape of motion, the meet with no truly articulate respouse. motive power being supplied by heat. All that can be said is that the ob- Apart from this stimulus it would be as served wide diversities of melting and inert as a locomotive with the steam boiling points result from an equally shut off. Matter in this state of hiberwide diversity in the conditions affect-nation, however, lies outside the scope ing the molecular equilibrium of the of terrestrial experience. Even at the substances severally concerned. As an lowest temperatures attainable by artiexplanation this is evidently unsatis- ficial contrivances, its particles thrill factory. It amounts to little more than with varied movements, which, as they a restatement of the same fact in differ- gain intensity through increase of heat, ent words. Yet the difference of word-tend to separate the molecules in oppoing is instructive; it implies a good sition to the cohesive force drawing deal. Let us consider and draw out its them together. Cohesion acts with meaning. The word "molecule " equivalent to little mass — was employed in 1811 by an Italian physicist named Avogadro, to designate the smallest particles of any substance solid, liquid, or of ex enormous power, but over a narrowly limited range. M. Quincke calculates that the mutual attraction of two molecules is insensible at distances ceeding one twenty-thousandth of a millimetre; yet within that minute interval its action is of amazing vigor. ities are preserved in their integrity. The irresistible energy of heat can, Molecules are not indivisible. They gaseous - in which its distinctive qual can be severed into "atoms" by the 1 1 Glazebrook, Properties of Matter, p. 119. it is true, unlock the grip of the | belongs to heat. Thermal energy immolecules; but only when lavishly parts the movements by which cohesion expended. The force consumed in is overcome. There is no substance so melting one pound of ice would suffice, obdurate but that it gives way before if mechanically applied, to lift it about the persistent attacks of the "drudging twenty-one miles from the ground; goblin of our laboratories. Even and the vaporization of the resulting platinum volatilizes in the electric arc pound of water would be a piece of at a temperature of about 4500° of work nearly seven times more arduous Fahrenheit. Intense cold, however, is again. Yet the large stores of heat much more difficult of production than thus employed in overcoming cohesive intense heat. And only by means of bonds produce no thermometric effects. | extraordinarily intense cold can truly They remain “latent" in the bodies aëriform substances be brought to subthey serve to modify, and are given mit to the yoke of internal attractions. out again in undiminished quantity Nor can they be mechanically comduring the inverse processes of lique-pelled to do so. Pressures up to twenty faction and solidification. Ther tons per square inch were, by Natterer, The differences between solid, liquid, in 1853, brought to bear upon large and gaseous bodies depend mainly upon volumes of hydrogen, oxygen, and nichanges in the relative mobility of their trogen, without the slightest effect in ultimate particles. These little sys- changing their state; and air has been tems, which are crowded by quadril- quite fruitlessly, so far as liquefaction lions into every cubic inch of matter, was concerned, condensed until heavare in all cases animated by movements ier, bulk for bulk, than water. of vibration, perhaps also of rotation mal activity must, in fact, be reduced. and even of orbital circulation; but below a certain definite point before under the strict rule of solidity they the passage of a gas into a liquid bepossess no proper motions; each has comes possible. This general principle its own place and keeps it. Liquefac- was recognized by Faraday in 1826, but tion, however, confers a translatory its detailed development by Andrews faculty. The molecules of fluids travel in 1869 constituted a fresh discovery of indefatigably. Let any one who doubts this to be a fact introduce a few drops of some colored tincture into a glass of water, and observe, after a time, the equable diffusion of the tint. He will no longer hesitate to admit the progress of incessant, undirected interstitial movements. Yet the qualified freedom of liquidity is bondage compared with the unrestricted license of the gaseous state. Here the last link with diminution of heat. In other of cohesive constraint is broken. Each words, this substance is, in the techminutest particle of an aëriform fluid nical sense, a gas when hotter, a vapor is not only virtually independent of the when colder, than 88°. No less than others, but strives towards definite sep- 144° of frost are, however, needed to aration from them. Hence a gaseous liquefy it under ordinary atmospheric mass forms of itself no definite surface. | pressure. At the sea-level, that is to If distributed in the shape of an atmo- say, carbonic acid boils in open vessels, sphere it may be coerced by gravity. at -112°. Water, as everybody knows, When evolved on the earth's surface it can be preserved only by being imprisoned; for its inner principle is one of limitless dispersion. The mastery over the states of matter the highest importance. He showed that above a certain fixed temperature, proper to each, aëriform fluids cannot assume the liquid state. Many of these "critical temperatures were determined by him. That of carbonic acid, for instance, he found to be 88° F. Above that point no compulsion avails to bring about liquidity; below it, pressure is effectual, and more readily reaches the corresponding stage 324° higher, at 212°; but its boiling point can, by means of continually increased 1 Barker, Text-Book of Physics, p. 319 pressure, be pushed up the scale as far | furnishing the pressure to which these as 773°. Red-hot water is thus a pos- results were due. The assistance of sibility; although in approaching, even cold was not invoked; aud, indeed, the distantly, the critical temperature above which it can only subsist as a gas, it becomes dangerously explosive. Volcanic outbursts are often, it is believed, immediately due to the sudden flashing into steam of superheated water. The critical temperatures of the various kinds of matter extend over a wider range than has yet been thermometrically explored. Those of some of the metals, as well as of carbon and silicon, must represent an enormous degree of heat; those of several gases have been ascertained to verge towards the lowest limit of cold. Their several positions depend upon the way in which the balance, in each particular case, inclines between the antagonistic forces of heat and cohesion. For, however closely the particles of a body may be constrained to approach each other, they will not cohere while in extra rapid motion. This doctrine is of grave significance to physical theory; and the guidance afforded by it is indispensable to the success of practical researches into the transformations of matter. Lavoisier divined the not too obvious truth that the "state" of any material substance is a mere question of temperature, and that consequently the socalled "permanent gases might, by extreme cold, be reduced liquids, and these again to solids. And Dalton wrote, in 1801: "There can scarcely be a doubt entertained respecting the reducibility of all elastic fluids, of whatever kind, into liquids; and we ought not to despair of effecting it in low temperatures, and by strong pressure exerted upon the unmixed gases. "1 The experimental verification of this forecast, now all but complete, was begun by Faraday. In 1823 he announced the liquefaction of chlorine; and he was similarly successful with carbonic acid, nitrous oxide, cyanogen, ammonia, and some other gases, their continued evolution in closed vessels 1 Quoted by Dewar, Proceedings Royal Institution, vol. viii., p. 657. difficult art of refrigeration was then in its infancy. Its wonderful progress in recent times may be said to date from Thilorier's production, in 1835, of solid carbonic acid. "Snow "" of this peculiar description might, so far as appearances go, have come from an Alpine nevé. Although cold enough to give a severe burn, it can be lightly handled with impunity, and is tolerably permanent even in warm air. Mixed with ether, it enabled Faraday to resume in 1844 his efforts towards condensation with the aid of temperatures as low as -166° F. Six gases, nevertheless, continued to hold their own. The chief of these were hydrogen, oxygen, and nitrogen; but the resistance of all except hydrogen has since been overcome. The liquefaction of oxygen by two independent investigators, Pictet of Geneva, and Cailletet of Paris, was announced to the French Academy of Sciences on the same day of December, 1877.2 Unknown to each other they had been working for several years along parallel lines. Their success was, indeed, determined by the use of an identical method. The gas, loaded with the weight of five or six hundred atmospheres at a temperature of about 130° F., was then suddenly allowed to escape through a narrow aperture. The ensuing violent expansion consumed a large quantity of heat, the abstraction of which from an adjacent portion of the same substance cooled it to the point of condensation, and liquid oxygen was for the first time seen on our planet. But only in a thin jet and during a few seconds. Its capture for examination was out of the question. |