WATER., no ITS PHYSICAL RELATIONS. In the preceding article the chemical history of water is briefly reviewed, and such of its pro perties are described as depend, primarily, on the nature and activity of the molecules of which it is constituted. We now proceed to treat of some of those properties of water which are exhibited by masses of it, whether in its liquid, ariform, or solid state ; those which render it a subject of physics or natural philosophy ; omitting, however, of course, such properties as it possesses in common with other bodies in the corresponding states of aggregation, respectively, and which have been considered in the articles HYDRODYNAMICS; HYGROMETRY; MECHANICS; PNEUMATICS, &C.
The three states of aggregation in which water, like all kinds of ponderable matter, an we have reason to believe, can exist, aro all equally natural; though, on in the case of every other substance also, we are inclined to regard that condition as the must natural in which it is most commonly and obviously subject to our observation. 7 his, with respect to water, is the liquid, as with all metals but One it is the solid, and with chlorine, ammonia, and other elementary as well as compound eubstancee, it is the atriform state ; omitting hem any reference to those gaseous bodies which have not yet been reduced to another state of aggregation, We begin with the physical properties of water in the solid form, considering, first, those which it manifests to sensible observation.
In the article ICE the property is described, in virtue of which two portions of that substance in a moist state, when brought into contact, become one. That such is the fact has of course been known from time immemorial, but it had always been referred, without inquiry, to the freezing effect 'upon water of ice at a lower tem perature [HAIL], and had never been made a subject of scientific investigation until Dr. Faraday called attention to its nature and philosophical importance on the 7th of June, 1850, at one of the Friday evening meetings of the members of the Royal Institution of Great Britain (Albemarle Street, London); assemblies in which, from the year 1825 downwards, so many new facts and applications in science and new interpretations of facts have for the first time been publicly made known, or first publicly demonstrated by experiment. To this
property of ice the term regelation was afterwards applied by Professor Tyndall, in a paper Structure and Motion of Glaciers,' by himself and Professor Huxley, read before the Royal Society on January 15, 1857 (' Proceedings,' vol. viii, p. 331), and published the Philosophical Transactions' for that year. In this paper Pro fessor Tyndall describes some experiments illustrative of the practical consequences of regelation, and of their manifestation on the great scale in nature. The entire subject forms so important a part of the history of water in its solid condition, that it is requisite to return to it here.
In the article Ice we noticed Professor Tyndall'e conclusion that the plasticity of ice at 32°,in mass, arising from fracture and regelation, iu continued and indefinite succession, imparts to it a deceptive semblance of viscosity, which it really does not possess. By virtue of this process, in his experiments, spheres of ice were flattened into cakes, and squeezed into transparent lenses. A straight prism six inches long was passed through a aeries of moulds augmenting in curvature, and finally came out bent into a semi-ring. A lump of clear ice placed in a hemispherical cavity, and pressed upon by a protuberance not large enough to fill the cavity; was converted iu to a hard transparent cup. In the experiments with the prism, four moulds, gradually augmenting in curvature, were made use of in succession. In passing suddenly from the shape of one to that of the other the ice was fractured, but the pres sure brought the separated surfaces again into contact, and caused them to (regelate) freeze together, thus restoring the continuity of the mass. The fracture was in every case both audible and tangible—it could be heard and it could be felt. A series of cracks occurred in succession as the different parts of the ice-prism gave way, aud towards the con clusion of the experiment the crackling iu some instances melted into an almost musical tone.