Mineralogy and Geology. 125 
siliceous organisms. “The usual method of burning the coal,” Dr. 
Schulz states, ‘‘is attended with an unavoidable vitrification of the 
mineral constituents, even when conducted in the slowest and most cau- 
tious manner, owing to which their cellular structure is lost. After 
many fruitless experiments I succeeded in hitting upon a method of 
incineration, which leaves the silica contained in the coal perfectly 
unaltered. Very instructive preparations are readily obtained (from 
the already known structural relations of siliceous earth in plants) on 
moistening grass-halms, ears of grain, Equisetum, Spanish cane, &c. 
with nitric acid, and afterwards burning them on platinum foil. The 
nitric acid not only facilitates the combustion of the organic substance, 
but also prevents the potash combined with the vegetable acid from be- 
ing converted into carbonate of potash before the silica has been heat- 
ed to such a degree as to be less liable to be acted upon. The greater 
degree of heat required for the perfect combustion of the coal no lon- 
ger destroys the cellular form of the silica after nitric acid has pre- 
vented the production of carbonate of potash on the first application of 
heat. An excess of nitric acid has the effect of destroying the con- 
nexion of the siliceous cells and acts too powerfully upon them, and 
should therefore be avoided. 
“Encouraged by the success of these experiments, I turned my 
"attention to coal, it being exceedingly desirable to be enabled to detect 
remains of organic structure in it. The large quantity of siliceous 
earth contained in all varieties of coal led me to infer that a judicious 
method of incineration would be attended with good results; your 
excellency will be enabled to judge from the preparation attached in 
how far I have succeeded. A piece of coal of about two square 
inches was broken into twelve pieces of nearly the same size, and then 
treated with nitric acid in a platinum vessel. The nitric acid being 
evaporated at a moderate heat, I ignited the residue until no further em- 
pyreumatic vapors were given off, treated the residue again with nitric 
acid and repeated the ignition. Thus prepared, the coal was placed in 
a platinum crucible with a lid perforated in the centre, and air was blown 
from a gasometer through the aperture in the lid, whilst the crucible 
was kept at a red heat overa spirit-lamp, so that the coal was necessa- 
rily slowly consumed. The ash thus obtained had not coked, but form- 
ed a brownish powder. Some white splinters occur among this, which 
appear on microscopical examination to be aggregated siliceous cells 
arranged in regelir succession, of the structure of the memes 
tous cells of wood.” : 
Prof. Exrenserc added, that the importance of a method for ebeatai 
ing the organized siliceous parts from the lower strata of the earth with 
their forms preserved for microscopicul observation is manifest, and 
