96 



Fossil Bones and Pseudo-Coprolites of the Crag. 



of fluorine was calculated. It was generally found necessary, in 

 order to ensure correct results,, to remove the last traces of fluoride 

 of silicon from the apparatus by means of an air-pump. 



The process just described, it will be immediately seen, is 

 essentially the same as that which was proposed some time since 

 by Professor Wohler (Poggendorff's Annalen, Band xlviii.). It 

 is, however, the best I am acquainted with, and by adopting the 

 few precautions I have noticed, so far as my own experience goes, 

 I think furnishes correct results. 



I will now proceed to detail the numerical results of my 

 analyses, premising that, some few of these have been already 

 made known to the public through the pages of another period- 

 ical ; but, in order to render the present memoir as complete as 

 possible, it was thought advisable to re-introduce them here. 



I. Phospkatic Earth. 



This mineral, which presented the appearance of a light yel- 

 lowish-brown powder, was sent to my father for analysis by a 

 gentleman resident in Exeter, v/ho stated that it was found in 

 large quantity in the green-sand and the lower strata of the chalk 

 formations of Sussex and Surrey. Some facts, however, that have 

 been recently brought under my notice induce me to believe that 

 it was nothing more than the powdered coprolites from the Suffolk 

 crag. 



The specific gravity, at 60° F., was 2-981. 

 The percentage composition was as follows : — 



Water 3-400 



Organic matter ...... traces. 



Silica, with some silicate of alumina and sili- 

 cate of iron . . . . . . 13-240 



Chloride of sodium ..... traces. 



Sulphate of soda ...... ditto. 



Carbonate of lime 28-400 



Carbonate of magnesia .... traces. 



Sulphate of lime ...... 0*736 



Phosphate of lime (tribasic) . . . . 21-880 



Phosphate of magnesia .... traces. 



Perphosphate of iron {2W 0^+3PS^) . . 24-760 



Phosphate of alumina 6*998 



Phosphate of manganese .... traces. 



Fluoride of calcium some. 



Loss 0-586 



100* 



II. Pseudo- Coprolites, 



«. The following are the analyses of two phosphoric nodules 

 from the coast of Suffolk. They were of an oval form, and 



