( lOO ) 



Some may pertaps wifh to enquire, whe- 

 tlier the roof of this cavern prefents any 

 of thofe ftaladical concretions which are 

 obfervable in many other excavations in 

 mountainous countries. No fuch concre- 

 tions are to be feen ; the ftone of which it is 

 formed being evidently not of an aqueous 

 but an igneous origin, that is, a lava diftin- 

 guifhed by the following charaders. 



Its bafe is fhoerl in the mafs ; it is mo- 

 derately porous, and therefore rather light ; 

 but gives fparks with fteel. It is unequal 

 in the fradtures, has a fomewhat argillaceous 

 odour, and attracts the magnetic needle at 

 the diftance of half a line. It is of a grey 

 colour; but interfperfed with white, fhin- 

 ing, rhomboldal feltfpars. Their fplendour 

 is diminifhed in the furnace ; but their 

 whitenefs appears heightened from the black 

 colour acquired by the enamel produced by 

 the fufion of the lava, which is opake and 

 extremely full of bubbles. The fufion, in- 

 ftead of diminifhing or deftroying, rather 

 increafes its magnetifm. 



This 



