



i6 ILLUSTRATIONS OF TH£l 



Now, a porous mafs of unconnedled materfaL%. 

 fuch as the ftrata appear originally to have been, 

 can acquire hardnefs and foliditj only in two 

 ways, that is, either when it is firfl reduced by 

 heat into a ftate of fufion, or at leaft of foftnefs, 

 and afterwards permitted to cool; or when matter 

 that is diflblved in fome fluid menftruum, is in- 

 troduced along with that menftruum into the 

 porous raafs, and^ being depofited, forms a ce- 

 ment by which the whole is rendered firm and 

 compa6l. Fire and water, therefore, are the 

 only two phyfical agents to which we can afcribe 

 the confolidation of the ftrata ; and, in order to 



h 



determine to which of them that effedl is to be 

 attributed, we muft inquire whether there are 



certain characters that diftinguifti the ac- 



tion of the one from that of the other, and 



which may be compared with the phenomena 



adually obferved among mineral fubftances* 



12. Firft, then, it is evident, that the con- 



4 



folidation produced by the adion of water, or 

 of any other fluid menftruum, in the manner juft 

 referred to, muft neceflTarily be imperfed, and 

 can never entirely banifti the porofity of the 

 mafs. For the bulk of the folvent, and of the 

 matter it contained in fokition, being great- 



+ 



er than the bulk of either taken fingly, when 

 the latter was depofited, the former would have 



fufBcient room left, and would continue to oc- 



cupy 



any 



\ 



