LIFE of Dr HUTTON. 47 



A good deal of his leifure was now employed in the profecu- 

 tion of chemical experiments. In one of thefe experiments, 

 which he has no where mentioned himfelf, but which 1 have 

 heard of from Dr Black, he difcovered that mineral alkali is 

 contained in zeolite. On boiling the gelatinous fubftance ob- 

 tained from combining that foflll with muriatic acid, he found 

 that, after evaporation, fea-falt was formed. Dr Black did not 

 recollect exactly the date of this experiment, but from circum- 

 ftances judged that it was earlier than 1772 : It is, if I miftake 

 not, the firft inftance of an alkali being difcovered in a ftony 

 body. The experiments of M. Klaproth and Dr Kennedy 

 have confirmed this conclufion, and led to others of the fame 

 kind. 



In 1774 he made a tour through part of England and 

 Wale*, of which, I find no memorandum whatever among 

 his papers. I know, however, that at this time he vifited the 

 falt-mines in Chefhire, and made the curious obfervation of 

 the concentric circles marked on the roof of thefe mines, to 

 which he has referred in his Theory of the Earth, as affording a 

 proof that the fait rock was not formed from mere aqueous 

 depofition. His friend Mr Watt of Birmingham accompanied 

 him in his vifit to the mines. 



It was after returning to Birmingham from Chefhire, that he 

 fet out on the tour into Wales. One of the objects of this tour, 

 as I learnt from himfelf, was to difcover the origin of the hard 

 gravel of granulated quartz, which is found in fuch vafl abun- 

 dance in the foil about Birmingham, and indeed over a great 

 tract of the central part of England. This gravel is fo unlike 

 that which belongs to a country of fecondary formation, that it 

 very much excited his curiofity ; and his prefent journey was 

 undertaken with a view to find out whether among the primi- 

 tive mountains of Wales, there were any that might be fuppo- 

 fed to have furnifhed the materials of it. In Wales, however, 



Vol. V.— P. III. G he 



