MINERALOGY. 6 9 



ef mountains. The chert is like wife found plentifully in 

 the neighbourhood of fcaly limefione, as flint is in the ftrata 

 of chalk. What connexion there may be between thefe bo- 

 dies, perhaps time will difcover. 



But flints and agates being always found in loofe and 

 iingle irregular nocuies, and never in rocks, as the chert, is 

 a circumftance very infufneient to eftabjiih a difference be- 

 tween them ; for there is agate near Conftantinople running 

 vein-like acrefs the rock with its country, of the fame hard- 

 nefs, and as fine and tranfparent as thofe other agates, which 

 are found in round nodules at Deux Ponts. We mult there- 

 fore content ourfelves with this remark concerning flints, That 

 they fcem to be the only kind of Hone hitherto known, of 

 which a very large. quantity has been formed in the fhape of 

 loofe or feparate nodules, each furrounded with its proper 

 cruil ; and that the matter which conltitutes this cruft, has 

 been fecarated from the reft of the iubftance in like manner 

 as fandiver, or glafs gall, feparates irom, and fwims upon 

 glafs during its vitrification ; tho' fometimes the formation of 

 this craft may have been prevented by the too fudden harden- 

 ing of the matter itfelf: I fhali therefore take the liberty 

 to call this matter of the crult, which fometimes is an in- 

 durated terre verte, by the name of Agate- gall. 



Other fpecies of it.or.es, which are tour.d in loofe pieces, 

 c nodules, except ores, and fome forts of ilaladlites, fhew 

 evidently by their cracks, angles, and irregular figures, that 

 they have been torn from rocks, i oiled about, and rubbed 

 again ft one another in torrents, or by fome other violent 

 motions of water. That flints have originally been in a foft 

 ftate, as i have mentioned, is eafy to be feen in the Egyptian 

 pebbles, which have impreflions of fmall ftones, fand, and 

 fometimes perhaps grafs, which however have not had any 

 ir.grefs into the very flint, but feem only to have forced the 

 abovecnentioned agate gall or cruil out of the way f . 



SECT. LXIV. 



G. Jafper, Jafpis. 



All the opaque flints are called by this 

 name, whofe texture refembles dry clay, and 

 which have no other known quality, whereby 



- The erroneous no'ionof 'he once foft ftateof ftones, fee difcuffed 

 in my Fifft Le£«ie on Fcffil.-. i). C. 



F 3 they 



