Constitution of the Ichthyolites of Stromness. 283 
potash, but no ammonia could, by the ordinary means, be de- 
tected. 
Having thus ascertained the presence of a large quantity 
of bituminous matter in the coal, a portion of the surround- 
ing rock was subjected to similar treatment, and, with like 
results, the bituminous matter, in the specimens examined, 
amounting to 18 per cent. 
After ignition, the remaining ash dissolved with effer- 
vescence in diluted hydrochloric acid, with the exception 
of a portion of siliceous matter. Ammonia added to the 
acid solution, caused a copious gelatinous precipitate, pre- 
senting all the characters of phosphate of lime. Oxide of 
iron was present in minute quantity, probably in combina- 
tion with sulphur, as traces of sulphuric acid were detected, 
when the ash was boiled with nitromuriatic acid. Chlorine 
could not be found. Carbonate of lime occurred in consider- 
able quantity, and magnesia was also detected. Soda and 
potash were sought for, but without success. 
A careful examination was instituted, in order, if possible, 
to detect the presence of fluorine, which is so constantly met 
with in fossil organic remains. Indeed, until of late, the 
researches of Rees, Girardin, and Pressier of Rouen, and 
others, seemed to indicate that the occurrence of fluorine 
was characteristic of fossils, and that it was not to be found 
at all as a normal ingredient of recent bones, as stated by 
Berzelius. More recently, however, the results of the ana- 
lysis of that celebrated Swedish chemist have been verified 
by the investigations of Dr Daubeny and Mr Middleton. 
On submitting a portion of the powdered coal to the action 
of a gentle heat, along with sulphuric acid, in a platinum 
crucible, covered with a plate of glass, coated on its lower 
surface with a thin layer of wax, in which lines were drawn 
with a pointed piece of wood, and kept cool by damp cloths, 
no traces of fluorine could be detected, the glass being left 
quite uncorroded. Having failed in this way, the powder 
was then ignited, as recommended by Dr Daubeny, in his 
- most valuable paper in the Philosophical Magazine, vol. xxv. 
No. 164; the ash dissolved in muriatic acid, the phosphates, 
(along with the fluates, if any were present), thrown down by 
