230 THEORY of the EARTH. 



the materials may be confolidated, in a fimilar manner, by the 

 fufion of their fubftance ; and foreign matter may be intro- 

 duced into the open ftruclure of ftrata, in form of fleam or ex- 

 halation, as well as in the fluid ftate of fufion ; confequently, 

 heat is an agent competent for the confolidation of ftrata, 

 which water alone is not. If, therefore, fuch an agent could 

 be found acting in the natural place of ftrata, we muft pro- 

 nounce it proper to bring about that end. 



THE examination of nature gives countenance to this fuppo- 

 fition, fo far as ftrata are found confolidated by every fpecies of 

 fubftance, and almoft every poffible mixture of thofe different 

 fubftances ; confequently, however difficult it may appear to 

 have this application of heat, for the purpofe of confolidating 

 ftrata formed at the bottom of the ocean, we cannot, from na- 

 tural appearances, fuppofe any other caufe, as having actually 

 produced the effects which are now examined. 



THIS queftion, with regard to the means of confolidating 

 the ftrata of the globe, is, to natural hiftory, of the greateit 

 importance ; and it is efTential in the theory now propofed to 

 be given of the mineral fyftem. It would, therefore, require 

 to be difcufled with fome degree of precifion, in examining 

 the particulars ; but of thefe, there is fo great a field, and the 

 fubjecl is fo complicated in its nature, that volumes might be 

 written upon particular branches only, without exhaufting 

 what might be faid upon the fubjecl j becaufe the evidence, 

 though ftrong in many particulars, is chiefly to be enforced 

 by a multitude of facts, confpiring, in a diverfity of ways, to 

 point out one truth, and by the impoflibility of reconciling all 

 thefe facts, except by means of one fuppofition. 



BtTT, as it is neceflary to give fome proof of that which is to 

 be a principle in our reafoning afterwards, I fliall now endea- 

 vour to generalize the fubject as much as poflible, in order to 

 anfwer that end, and, at the fame time, to point out the par- 

 ticular method of enquiry. 



THERE 



