BISTORT of the SOCIEfr. 9 



veins "one connected and uninterrupted mafs, mud have flowed 

 in a foft or liquid ftate into its prefent pofition. 



In giving an account of thefe obfervations, Sir James Hall 

 was led, by finding it impoffible for him to exprefs his ideas 

 clearly on the' fubject, to enter at confiderable length into a dif- 

 cuffion of the terms of mineralogy, the imperfection of the 

 language of that fcience, and the principles on which a lefs am- 

 biguous nomenclature might be formed. He particularly 

 pointed out, as the bans of fuch a nomenclature, the grand di- 

 vifion which nature has made in the mineral kingdom, into 

 ftratified and unftratified bodies, the former comprehending 

 both the primary and fecondary ffrata, the latter comprehend- 

 ing granite, porphery, bafaltes, trap or whinftone, and lava. 



He next ftated the argument which the facts concerning 

 granite that have been referred to above, afford in fupport of 

 Dr Hutton's Theory of the Earth. He remarked alfo the 

 great number of facts which he had met with in Scotland, and 

 in the volcanic countries of Italy, that were connected and ex- 

 plained by that theory, and by no other ; concluding on the 

 whole, that there was fcarcely any fyftem in phyfics eftablifhed 

 on more folid principles, and that the publication of it was 

 likely to form a very important epoch in the hiftory of this 

 branch of philofophy. 



To a theory, however, which embraces fo great a variety of 

 objects, fome difficulties muft be expected to occur ; and this 

 is the more likely to happen, that though the agents employed 

 in it be fuch as we are well acquainted with, yet they are in- 

 troduced as acting in circumftances very different from thofe 

 in which we ufually fee them act. 



Of thefe difficulties the mod confiderable appeared to Sir 

 James Hall to be the following : In granites which contain 

 quartz and felt-fpar, it frequently occurs, that the felt-fpar is feen 

 with the form of its cryftak diflinctly defined, whilft the 

 quartz is a confufed and irregular mafs, being almofl: univer- 



Vol. III. (B) fally 



