451 



of action which is manifested in regelation ; ancl " many such like 

 cases," he remarks, " may be produced." In his reasoning on the 

 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 Desormesf. 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, ex- 

 tensive 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 



* Exp. Res. in Chemistry and Physics, pp. 380, 381. 



f As far as my reading extends, it was first recorded by Pouillet in his ' Ele- 

 mens de Physique/ liv. vi. ch. ii. 2 me edit. Paris, 1832, tome iii. p. 41 (Bruxelles, 

 1836, p. 292). In the fourth edition, Paris, 1844, it appears to be omitted, toge- 

 ther with other and established facts relating both to glass and to metals. 



