( 20 ) 



to afcertain Its depth. But in every place 

 where I could difcover the bottom, I oh- 

 ' ferved that it reded on a bed of pumices, 

 partly pulverized, and partly in detached 

 pieces approaching to the globofe form. 

 They belong to the clafs of the lighteft of 

 thefe fubftances. It appear?, therefore, in- 

 dubitable that thefe pumices had been 

 thrown out of the burning mouth of fome 

 volcano, before the flowing of the tufaceous 

 current. 



This tufa prefented a very unexpected 

 phenomenon. On breaking it, its fradures 

 exhibited frnall black particles, which were 

 diftinClly recognized to be true coal, from 

 t their blacknefs, lightnefs, drynefs, the faci- 

 lity with which they broke, and their fmall 

 degree of hardnefs. Some of them, like- 

 wife, when expofed to fire in the open air, 

 fumed, and became red hot ; others emitted 

 a little flame. The latter had not been 

 perfed.ly reduced to coal, as the fibrous 

 parts of the wood were Itill to be feen. 

 Thefe coals were fmall cylinders from two 



or 



