20 
SALOON. 
Nat. Hist. 
Jew specimens of the less compound varieties of 
agates, in which common calcedony, carnelian 
and heliotrope respectively form the predominant 
ingredients.—Of flint, a well known mineral 
substance, several interesting varieties are depo¬ 
sited in this case. 
(Case 8.) Contains principally opaline sub¬ 
stances, viz. specimens of the noble opal, which 
owes its beautiful play of colours to a multipli¬ 
city of imperceptible fissures in its interior ; the 
Mexican sun or fire opal; the common opal, 
a translucent white variety cf which, appearing 
yellow or red when held between the eye and the 
light, is called girasol ; the semi-opal, agreeing in 
its principal characters with the common ; speci¬ 
mens of those varieties which, havingthe property 
of becoming transparent when immersed in water, 
arecalled hydrophanes, and vulgarly oculus mundi; 
wood opal, or opalized wood ; jasp-opal, referred 
by some authors to jasper; the menilite, called 
also liver-opal, found at Menil-Montant, near 
Paris, in a bed of adhesive slate, a specimen of 
which is added. Some varieties of cacholong 
may likewise be referred to the opal-tribe.—The 
remainder of this case is occupied by the siliceous 
substance called hornstone, divided into thecon- 
ehoidal and splintery varieties ; among these are 
the remarkable pseudomorphous crystals from 
Schneeberg, 
