It is observed in the concluding Note,' that " No crystalline body baa been longer or more extensively subject to human observation than era-eternised water, or ice. Its natural history and properties, as science has advanced, have been investigated with increasing generality and precision ; and they have finally become objects of that systematic and exact research which characterises the present era of physical inquiry A most remarkable deficiency, however, still remains, apparently, in our knowledge of this substance : water is the vitreous condition—Ice glass—has never been observed. While wo know the antithetical vitreous state of so many different crystallised substances, —minerals produced by heat, salts deposited from aqueous solution, neutral bodies of organic origin,—and have great reason to believe that that antithetical condition to crystallisation is universal, we have no knowledge of it in relation to water or ice. My own attention has been awake to the subject, without success, for many years. It would seem to be scarcely within the bounds of possibility that the glassy state of water, if possessing what we term solidity, should not, ere now, either have been observed in nature, or have occurred and been recognised in experimental research." Mr. Brayley inquires, "Does this apparent deficiency in our know ledge exist because—to use lauguage recently introduced into physical science—the homologue of the glassy state of water is not what we ordinarily term solid—because the state of water cooled below 32°, but still liquid, is in fact the state which corresponds to the vitreous con dition of other bodies, and to the physical nature of perfect ordinary glen! Is the one simply a case of potential solidity, and the other of the confluent or equivalent state of arrested liquidity!" In reply to the anticipated objection that the homology sought to be established between liquid water below 32° and glass, is a forced one, and after admitting that, in relation to each other, these are extreme cases, he proceeds to show that intermediate terms of the series are not wanting, some of them being supplied by sulphur and phosphorus, and others, in a remarkable manner, by selenium, various conditions of all three appearing to be homologues, at once, of both the extreme terms here alluded to. Mr. Brayley suggests, finally, " Should this hypothesis be verified, water below 32°,—or rather, perhaps, from the temperature of maximum density downwards through that of freezing,—may have to be regarded as the vitreous condition of matter; and the causes of the peculiar characters of that condition, its effects on the transmission of the vibrations of sound and light, the coochoidal fracture, &c., may have to be discovered by researches on its molecular nature." In expositions, whether of the progress or the actual condition of any branch of science, the student is perpetually reminded of the lesson which teaches the indissoluble and universal connection of every part of nature with every other part. Subsequently to the enunciation of all the views on the subject of regelation, and the mole cular relations of ice and water, of which an account has been given in the preceding columns, this truth has been exemplified in a striking and Instructive manner, which may eventually make it requisite to modify all existing conclusions on that subject and Its applications to natural phenomena.
In the' Proceerlinga of the Royal Society' for June ]3 of the present year (1861), vol. xi., pp. 243.247, appears the abstract of an elaborate paper titself to be published in the Philosophical Tninsactions ') on • Liquid Diffusion applied to Analysis,' by Mr. 'Thomas (late Professor) Graham, N'.P.R.S., 3laster of the Mint. In this be shows the value of the process of diffusion and of the principle of diffusibility In water, as affording the means of bringing out clearly the distinctive properties of what appear, in his judgment, to be two great divisions of chemical substances. Mr. Graham's former researches on DIFFUSION have bcvn noticed in the article on that subject As this will be the only oppor. tunity the near completion of our work will allow of giving an account of his new results, we shall cite so much of his abstract as, in addition to what is required for the subject of the present article, will suffice for that purpose. The entire subject of diffusion, wo may add, illus trates in a remarkable manner the importance of that perfect neutrality, as a chemical agent, which has been shown to characterise water in the preceding article on its chemical history.
"The first, or diffusive class of substances are marked by their tendency to crystallise, alone or in combination with water.
When in a state of solution they are held by the solvent with a certain force, so as to affect the volatility of water by their presence. The solution is generally free from viscosity, and is always sapid. Their reactions are energetic, and quickly effected. This is the class of crystalloids." " The other class, of low diffusibility, may be named colloids, as they appear to be typified Ly auimal gelatine. They have little, if any, tendency to crystallise, and they affect a vitreous structure. The planes of the crystal, with its hardness and brittleness, are replaced in the colloid by rounded outlines with more or less softness and tough ness of texture. Water of crystallisation is represented by water of gelatination. Colloids arc held in solution by a feeble power, and have little effect on the volatility of the solvents. The solution of colloids has always a certain degree of viscosity, or gumminess, when concen trated. They appear to be insipid, or wholly tasteless, unless when they undergo decomposition upon the palate, and give rise to sapid crystal loids. They are united to water with a force of low intensity. Although chemically inert in the ordinary sense, colloids possess a com parative activity of their own, arising out of their physical properties. While the rigidity of the crystalline structure shuts out external impreissions, the softness of the gelatinous colloid partakes of fluidity, and enables the colloid to become a medium for liquid diffusion, like water itself. The same penetrability appears to take the form of a capacity for cementation in such colloids as can exist at a high tem perature. Hence a wide sensibility on the part of colloids to external agents." "Another eminently characteristic quality of colloids is their muta bility. Their existence is a continued metastasis. A colloid may be compared in this respect to water while existing liquid at a temperature below its usual freezing point, or to a supersaturated saline solution. The colloidal is, in fact, a dynamical state of matter; the crystalloidal being the statical condition." " For the separatiou of unequally diffusive crystalloids from each other, jar-diffusion was had recourse to. . . . The separation of a crystalloid from a colloid is more properly effected by a combination of diffusion with the [osmotic] action of a septum composed of an iusuluble colloidal material. . . . This separating action of the colloidal septum is spoken of [in Mr. Graham's paper] as dialysis." " lee at or near its melting point appears to be a colloidal substance, and exhibits a resemblance to a firm jelly in elasticity, the tendency to rend and to redintegrate on contact" Regelation, according to this view, is the form in which the property of redintegration, belonging to all colloids, is exhibited by ice.* The truth of the view of the nature of ice, at or near its melting point, thus taken by 31r. Graham, will require to be tested by optical means, by which it must bo ascertained that, at those temperatures, it really is not a crystallised body. A further verification may be oh Lained by determining whether the alleged colloidal ice resists the passage of electricity as crystalline ice is known to do, and what changes the non-conducting power of the latter undergoes, during the reciprocal conversion of the crystalloid into the colloid state, until it becomes the conducting power of liquid water. (Faraday, 'Exp. Rea. in Elect.' par. 403.) Should its truth be established, Mr. Graham will probably be admitted to have discovered the key to the explanation of all the conflicting statements and theories respecting the nature of regelation and of the motion of glaciers. Ice, together with many other bodies, and perhaps all, will be Loth a colloid and a crystalloid. That which Dr. Faraday, in his recent experiments, found to have the flexible adhesion, will prove, in this case, to be the colloidal or vitreous form of that substance (ice-pleas, in fact ; almost identical with Mr. lirayley's homologue of that hitherto hypothetical body, as evinced by facts; recorded by Mr. Graham, which will presently be adverted to), while the rigid adhesion will be found to characterise its crystalloidal form; and the circumstances from which ho inferred that the former has not in reality the propertied of sticking and tenacity—in short, those of a viscous substance, will be found to arise from the constant and rapid passage—the metastasis of Graham—of the colloid into tho crystalloid body.