2jo THEORY of the EARTH. 



, THAT the contained fubftances mufl have been in a fluid 

 ftate, in order to their cryftallizing. 



Loflly, THAT as this fluid flate had not been the effect: of fo- 

 lution in a menftruum, it muft have been fluidity from heat 

 and fufion. 



THKRE are in jafpers and agates many other appearances, 

 from whence this lafl conclufion may be formed with great cer- 

 tainty and precifion ; but it is hoped, that what has been now 

 given may fufHce for eftablifhing that propofition without any 

 doubt. 



IT muft not be here objected, That there are frequently 

 found filiceous cryftals and amethyfts containing water ; and 

 that it is impoffible to confine water even in melted glafs. It 

 is true, that here, at the furface of the earth, melted glafs can- 

 not, in ordinary circumftances, be made to receive and inclofe 

 condenfed water ; but let us only fuppofe a fufEcient degree of 

 compreflion in the body of melted glafs, and we can eafily 

 imagine it to receive and confine water, as well as any other 

 fubftance. But if, even in our operations, water, by means 

 of compreflion, may be made to endure the heat of red hot 

 iron without being converted into vapour, what may not the 

 power of nature be able to perform ? The place of mineral 

 operations is not on the furface of the earth; and we are not 

 to limit nature with our imbecility, or eftimate the powers cf 

 nature by the meafure of our own. 



To conclude this long chemico-mineral difquifition, I have 

 fpecimens in which the mixture of calcareous, filiceous and 

 metallic fubftances, in almoft every fpecies of concretion which 

 is to be found in mineral bodies, may be obferved, and in 

 which there is exhibited, in miniature, almoft every fpecies of 

 mineral tranfaction, which, in nature, is found upon a fcale of 

 grandeur and magnificence. They are nodules contained in 

 the whinftone, porphyry, or bafaltes of the Calton-hill, by 

 Edinburgh ; a body which is to be afterwards examined, when 



it 



