J. W. Bailey on Camphor, Infusoria and Sulphur. 351 
the general form of the shells. These may sometimes but not 
generally be detected even in the fossil specimens. When pres+ 
ent, they materially interfere with the examination of the true 
nature of the markings of the siliceous shell, and should be de- 
stroyed by nitric acid and heat, before the hydrofluoric acid is 
employed, unless it is desired to study the cell-membrane itself. 
There is a curious difference in the action of hydrofluoric acid 
of the same strength upon specimens of fossil Diatomaceee from 
different localities. Some dissolve with even too great rapidity 
in an acid which is slow and tedious in its action on other speci- 
mens. The Bermuda and Richmond Tripoli, and some speci- 
mens of fluviatile origin resist the action much longer than is 
ustial with most specimens, whether they are recent marine, or 
either recent or fossil fluviatile ones. This difference is proba- 
* 
3. Mode of distinguishing artificial from natural Camphor 
of fine specimens of marine siliceous Infusoria or Diatomacee. 
_ The mud upon this ice is probably in part scraped from the sur- 
face of the flats, and partly derived from the filtering of the 
&e. The Co- 
Scinodiscus I have found in a living state as far up the river as 
most abundantly. ; a 
5. On the detection of Sulphur.—Dr. Playfair’s beautiful salt, 
the nitro-prussid of soda, is justly recommended by its discov- 
eret.as the most delicate of all tests for alkaline sul phids [sul- 
~ phurets].* An application of it which is very obvions although 
hot alluded to by Dr. Playfair, is to employ it not only as a di 
4 
— ©. ® Se Li E.and D. Phil Mag, vol. xxxvi, p. 208. 
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