Miscellaneous. 69 
On the Microscopic Constituents of the Ash of Fossil Coal. 
By Professor Enrenpere. 
At the meeting of the Berlin Academy of the 25th of October, Prof. 
Ehrenberg communicated an observation of Dr. Franz Schulz of 
Eldena, which the latter had addressed to M. v. Humboldt in a letter, 
in which he describes his method of separating the silica contained 
in coal so chemically pure as to enable us to recognise the microsco- 
pical siliceous organisms. ‘‘The usual method of burning the 
coal,” Dr. Schulz states, “is attended with an unavoidable vitrifi- 
cation of the mineral constituents, even when conducted in the 
slowest and most cautious 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 con- 
tained 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 burn- 
ing 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 being converted into carbo- 
nate of potash before the silica has been heated 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 longer destroys the cellular 
form of the silica after nitric acid has prevented the production of 
carbonate of potash on the first application of heat. An excess of 
nitric acid has the effect of destroying the connexion 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 at- 
tention 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 judi- 
cious method of incineration would be attended with good results ; 
your excellency will be enabled to judge from the preparation at- 
tached 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 empyreumatic vapours were given off, treated the resi- 
due 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 aper- 
ture in the lid, whilst the crucible was kept at a red heat overa 
spirit-lamp, so that the coal was necessarily slowly consumed. The 
ash thus obtained had not coked, but formed a brownish powder. 
Some white splinters occur among this, which appear on microsco- 
pical examination to be aggregated siliceous cells arranged in regular 
succession, of the structure of the prosenchymatous cells of wood.” 
Prof: Ehrenberg added, that the importance of a method for ob- 
taining the organized siliceous parts from the lower strata of the 
earth with their forms preserved for microscopical observation is ma- 
