SIR JAMES HALL on the Consolidation of the Strata. 329 



presents itself of incipient crystallisation, if I may use this term ; 

 a number of large, shining, parallel faces pervade the whole mass, 

 and, by holding the specimen at the proper angle to the light, 

 this appearance becomes very obvious. What the nature of these 

 crystals is, I have not investigated ; but as they very much re- 

 semble what we see in different kinds of sandstone, I am of opi- 

 nion that they hold out a fair expectation, of our being able to 

 produce many of the crystalline appearances with which we are 

 familiar in nature. 



Common sea-salt, such as I have used, as is well known, is 

 not pure muriate of soda ; and, in my experiments, I have mixed 

 various other substances with it. In Nature, we must suppose 

 that various contaminating substances would in like manner oc- 

 cur, to diversify the phenomena ; and, accordingly, we do find a 

 boundless variety, in the aspect not only of sandstone, but of al- 

 most every kind of rock ; and I am by no means without ex- 

 pectation, that, in the course of time, we shall be able to imitate 

 in our laboratory as many of these varieties as we choose to ex- 

 hibit. 



I have long been engaged also in a series of experiments on 

 the formation of Crystallites, the name by which, as I have be- 

 fore stated, every crystallised rock might, perhaps, be usefully 

 distinguished in contradistinction to Aggregates, or those formed 

 of fragments. This great object in experimental geology, I hope 

 to accomplish by means of an instrument which I have long had 

 in use, for the regulation of high heats, a description of which 

 may probably soon be laid before the Society, together with 

 some further results in support of the Huttonian Theory of the 

 Earth. 



x.t 2 



