195 
TAB. CCXCVIII. 
SILEX Quartzum, var. spongiosum. 
Swimming Quartz. 
Div. 2. Imitative. 
Tuis curious formation of Quartz differs very much from 
the last, and is therefore essential to this work, as it could 
scarcely have been thought to be the same substance. In- 
deed it might have been imagined as great a miracle to see 
Quartz float in a large mass as the iron ax’s head that Elisha 
caused to swim.—Masses of much larger dimensions than 
this now figured will swim, and scarcely displace the water. 
The present specimen ig too tender to bear handling, 
and is thinner than any paper. It seems to have been 
formed. in the interstices of some substance now entirely 
decomposed from it, which would appear to have 
had many thin cracks or flaws in it, crossing at various 
angles. I could not detect the cast of any thing regular 
about which it might form. I have some specimens very 
much resembling the crumb of bread. 
