224 'THEORY of the EARTH. 



diftant events; confequently, of difcovering, in the general 

 powers of nature, caufes for thofe events of which we fee the 

 efFeds. 



THAT the confolidating operation, in general, lies out of the 

 reach of our immediate obfervation, will appear from the fol- 

 lowing truth : All the confolidated maffes, of which we now 

 enquire into the caufe, are, upon the furface of the earth in a flate 

 of general decay, although the various natures of thofe bodies 

 admit of that diflblution in very different degrees *. 



FROM every view of the fubject, therefore, we are directed 

 to look into thofe confolidated mafTes themfelves, in order to 

 find principles from whence to judge of thofe operations by 

 which they had attained their hardnefs or confolidated (late. 



IT muft be evident, that nothing but the moft general ac- 

 quaintance with the laws of acting fubftances, and with thofe 

 of bodies changing by the powers of nature, can enable us to 

 fet about this undertaking with any reafonable profpect of fuc- 

 cefs ; and here the fcience of Chemiflry muft be brought parti- 

 cularly to our aid ; for this fcience, having for its object the 

 changes produced upon the fenfible qualities, as they are called, 

 of bodies, by its means we may be enabled to judge of that 

 which is poflible according to the laws of nature, and of that 

 which, in like manner, we muft confider as impoflible. 



WHATEVER conclufions, therefore, by means of this fcience, 

 fhall be attained, in juft reafoning from natural appearances, 

 this muft be held as evidence, where more immediate proof 

 cannot be obtained j and, in a phyfical fubject, where things 

 actual are concerned, and not the imaginations of the human 

 mind, this proof will be confidered as amounting to a demon- 

 ftration. 



PART 



* STALACTICAL and certain ferruginous concretions may feem to form an exception 

 to the generality of this propofition. But an objection of this kind could only arifc 

 from a partial view of things ; for the concretion here is only temporary, it is in confe- 

 quence of a folution, and it is to be followed by a diflblution, which will be treated of in 

 its proper place. 



