TRANSACTIONS OF THE SECTIONS. 39 



As an experimental illustration, he took a piece of pretty rich sul- 

 phuret of copper and placed it in a narrow glass vessel, half filled with 

 sulphate of copper in solution ; the sulphuret was immersed about half 

 its length in this solution ; common water, with a few drops of acid, 

 was then added in the manner before stated, taking care that it should 

 not intermingle with the cupreous solution underneath. The whole was 

 then placed in the dark, and left untouched for about a week. 



At the end of that time Mr. Spencer examined it, and had the satis- 

 faction of observing that several portions of it had become covered with 

 very minute crytals of the pure metal : at the end of a fortnight still 

 more beautiful crystals had been deposited. 



This experiment was repeated with water taken from a copper mine 

 in Anglesey and with similar results. 



These experiments were adduced by the author in support of the 

 views of Mr. Fox. 



Mr, Spencer exhibited a Cylindrical Battery, so as to include great 

 intensity in small space. 



On the Artificial Crystallization of certain Metallic Carburets, as 



extensive of the Theory of Crystallization. By Samuel Brown, 



M.D..> Edinburgh. 



The theory of the circumstances in which the phenomenon of cry- 

 stallization takes place, so far as these have been hitherto known, may 

 be expressed in these three practical maxims : 



1st. When a body is slowly reduced to solidity from a state of 

 fluidity (gasiform or liquid), its particles congregate in such a manner 

 as to produce the crystallization of the substance concerned. This 

 includes crystallization by sublimation, fusion, and all the modifica- 

 tions of these processes. 



2nd. When a body is slowly deposited in the form of solidity from 

 a state of solution in a fluid (gasiform or liquid), its particles mutually 

 arrange themselves in the crystalline mode of cohesion. This com- 

 prehends all cases of simple crystallization, as effected by the gradual 

 elevation or depression of the temperature of solutions, and by the 

 evaporation or dilution of the solvents. 



3rd. When an insoluble solid body is slowly formed, whether by 

 synthesis or analysis, in a fluid, its particles assume the crystalline dis- 

 position about each other. To these the author adds a fourth. 



4th. When the particles of a solid body are slowly evolved from the 

 decomposition of a substance of which it, or its elements, are chemical 

 constituents, they cohere in crystal, and that independently, both of 

 the fusion or solution of the body crystallized, and of the presence of 

 any fluid medium of molecular motion whatsoever. Thus, when an 

 infusible metallic carburet is slowly formed in a shut vessel from the 

 decomposition of the cyanide, it is procured of a transparent, very hard, 

 and crystalline structure. 



