64 NOTE ON THE PRINCIPLE OF REGELATION, ETC. 
nature of that principle, he also rests on the fact, that ice has the 
same property as camphor, sulphur, phosphorus, metals, &c., which 
cause the deposition of solid particles upon them from the surrounding 
fluid, that would not have been so deposited without the presence of 
the previous solid portions.* 
In reflecting on these indications of the universality of the cause, 
whatever it may intrinsically be, which is operative in the phenomena 
alluded to, it occurred to me that the known fact of the incorpora- 
tion of two or more plates of glass into one block, presented a curious 
parallel to the incorporation of two or more slabs or separate portions 
of ice into one mass; and to determine in what manner these sub- 
jects were related to each other appeared to deserve careful investi- 
gation. Towards this the following suggestions are offered :— 
Certain substances, both elementary and compound, appear to 
present, in what we term the solid state, phenomena corresponding 
to those which are presented by others in the liquid and solid states 
and the transitions from one to the other collectively regarded, and 
indicating the existence of a condition of matter which may be termed 
arrested liquidity, but yet is not, in the most perfect sense, solidity. 
Of these bodies glass is one. The fact in question, which exemplifies 
in a striking manner the property here alluded to, appears to have 
been first noticed as a subject of scientific importance by MM. 
Pouillet and Clement Desormes.f It is the incorporation, into one 
mass, of two or more plates of the kind of glass manufactured for 
mirrors, and called plate-glass, the polished surfaces of which have 
been placed, and have remained for some considerable time, at common 
temperatures, in close contact with each other, the entire area of one 
plate being in contact with the entire area of the contiguous one,— 
extensive mutual surfaces of contact being thus supplied. Under these 
circumstances, two, three, or four, or even a greater number of plates 
become converted into one block of glass, which it is impossible to 
separate into the original plates, and which may be worked, and even 
cut with a diamond, asif the whole had originally been a single mass. 
In some specimens which I have examined, with the surface of one 
plate were incorporated portions of another, the surfaces of fracture of 
* Exp. Res. in Chemistry and Physics, pp. 380, 381. 
+ As far as my reading extends, it was first recorded by Pouillet in his ‘ Elémens de Phy- 
sique,’ liv. vi. ch. ii. 2me édit. Paris, 1832, tome iii. p. 41 (Bruxelles, 1836, p. 292). In the 
fourth edition, Paris, 1844, it appears to be omitted, together with other and established 
facts relating both to glass and to metals. 
