M. Keilhau's Theory of Granite, and other Rocks, 93 



tioned, but which, though it has been long employed, and 

 therefore must have been for a considerable period known to 

 chemists, has yet never been accurately examined. I allude to 

 a certain mode of treating poor copper-ores, described many 

 years ago by the Italian geologist Breislak, and employed in 

 Scandinavia as well as at Agordo in Italy. It consists in bring- 

 ing, by a proper degree of heat, but which, in order that the 

 process may succeed, must not go the length of causing smelting, 

 the greater part of the pure copper into the middle of a mass of 

 ore, while portions of the iron and sulphur contained in the 

 crude ore seem to be driven outwards. The copper, previously 

 only in the state of copper-pyrites, which was more or less uni- 

 formly disseminated through the whole mass, is now found in 

 the interior as a kernel, and exhibits a compound resembling 

 variegated copper-ore, or a mass even richer in copper. Give 

 this phenomenon what explanation you please, still it unques- 

 tionably belongs to that group of facts which teach us the pos- 

 sibility of such considerable chemical and morphological changes 

 in what are called rigid bodies, that, in the hypothesis we seek 

 for, we are not under the necessity of taking for granted, that, 

 for example, the substance of granite, immediately before the 

 formation of that species of rock, must have existed in a fluid 

 state, whether in a Neptunian liquid condition as a melted mass, 

 or in general in any of the modes of fluidity hitherto commonly 

 known ; for if it should be said that the case we have quoted 

 does not exclude the possibility that the transposed substances 

 might have been in a state of elastic fluidity, yet, even if this 

 could be shewn, the conceptions we have hitherto formed with 

 regard to this state must be not a little modified, namely in this, 

 that we must consider substances in this form as much more 

 adapted to penetrate and to move in solid masses than we have 

 hitherto believed them capable of doing. The following are also 

 examples of the processes of which we speak, viz. — of the crys- 

 tallization of and in solid masses : the transition of compact 

 substances, such as glass, amorphous limestone, &c. into a 

 crystalline state by the action of a moderate heat ; and the con- 

 version of barley-sugar from an imcrystalline to a crystalline 

 condition; of chemical changes without crystallization: the con- 

 version of various minerals into steatite (Speksteen,) 



