284 Dr Andrew Fleming on the 
ammonia, and the precipitate, after being thoroughly washed 
and dried, submitted as before to the action of sulphuric acid, 
in a platinum crucible, covered with a plate of glass prepared 
in the manner above described. No heat was applied, the 
temperature being raised sufficiently high by the chemical ac- 
tion, and the glass plate was left on the crucible for six hours. 
On removing it, at the end of that period, distinct marks 
of the corrosion of the glass were observed, leaving no doubts 
as to the presence of fluorine in the substance under exami- 
nation. I may here state, that, in this way, I have detected 
fluorine, with the greatest facility, in fossil bones from the 
rock of Gibraltar, in sharks’ teeth from the London clay, and 
in a portion of a fossil bone from Tilgate forest. In two 
specimens of recent human bones, the one a femur, and the 
other an os ilium, fluorine was detected in the phosphates 
obtained in the way before mentioned. 
The chief constituents, therefore, of these crusts of coaly 
matter are, phosphate of lime, carbonate of lime, and bitu- 
minous matter. 
A qualitative analysis having thus been executed, it was 
thought desirable that the proportion of the different con- 
stituents should be ascertained ; and for this purpose a care- 
fully selected specimen was pounded, which, after drying 
over a water bath, weighed 9.2 grs. This was ignited for 
some time in a platinum crucible, and was found to have lost 
4.32 grs. of bituminous matter. The ash was then treated 
with weak muriatic acid, which dissolved all, except a por- 
tion of silica (sand), which, when separated by filtration, 
washed and ignited, weighed 1.206. The phosphate of lime, 
precipitated by ammonia from the acid solution, weighed 
1.998 grs. The lime was thrown down as oxalate, and, 
after careful ignition in the usual way, amounted to 1.208 
gers. of carbonate of lime. To the remaining liquid, when 
reduced by concentration to a small bulk, phosphate of am- 
monia was added, and the precipitated magnesia, after igni- 
tion, weighed .594 grs. as phosphate, which corresponds to 
450 grs. of carbonate of magnesia. 
We have thus in a hundred parts :— 
