[ xviii ] 
the red are compounded, although this cannot 
yet be perfeftly proved to a demonftration. 
The hnji Nature are not feparateiy treated 
herein | they may be found every where in the 
Effay, becauie the rock cryftals do not appear 
to me lefs curious than the indurated marles ; 
and kidney o^e is often found of a morp 
furprifing figure than the eagle-ftone. I can- 
not therefore find any reafon for forming a 
clafs of them, nor do I comprehend what 
others take to be a greater pr lefs Iport of na^ 
tore in the mineral kingdom. 
Figured ftonesj or which contain the repre-? 
fentations of vegetables, animals, See. occafion- 
ed by different veins or colours^ in the ftones., 
are in my opinion of ffill lefs confequence, and 
^re alfo more difficult to range properly in 
ciaffes becaufe people feldom, or rather never, 
agree in faeir fancies s but what feems to re- 
prefent an objedl to one, may make a different 
appearance in the imagination of another, 
whereby both confufion and difputes would 
arife about the bodies of fuch a clafs, Befides, 
^ very fmall advantage, if any, can refult from 
fuch a clafs i fiiice all that the Almighty 
created has required equally his power, and is 
alfo equally worthy of our admiration : It gives 
rather rife to pedantry, whereby the attention 
is by degrees diverted from true knowledge to 
mere trifles, of which both ancient and mo- 
dern books are fad inftances ; and if Mr. Du 
Fay had not impeded the evil by difeovering the 
pteffiod of improving the figures upon flints 
