424 Dr. Prout on Vegetable and Animal Substances. [DxEc. 
margin ; but it is principally remarkable for a strongly prominent 
three-sided projection, something like an irregular, ill-shaped 
tetrahedron, one point of whose base is exactly at the point of 
the umbo of the hinge, and the two others are directed towards 
the two corresponding sides of the margin. I strongly suspect 
that this projection has been rendered unnaturally prominent by 
being rather laterally compressed. Fig. 10 is an indistinct frag- 
ment of the impression, probably of the lower valve of an hyste- 
rolite. Fig. 12, a bit of slate, which contains some pyrites, and 
upon which is an impression very much like that of the scale of 
the cone of some species of pinus; but it is quite impossible for 
me to decide whether it is an animal or vegetable remain. Fig. 13 
has the appearance of the outside of a bivalve shell, but it is 
extremely indistinct, and I dare not venture a conjecture upon 
it. Fig. 14, part of an impression of the outside of one valve of 
a bivalve shell, but to what genus it is referrible, I do not know; 
probably a Venus oracytherea. Fig. 15, a very indistinct sec- 
tion of a madrepore. Iam, Gentlemen, yours, &c. 
G. B. SowErRBy. 
ArTICLE II. 
On the Ultimate Analysis of Vegetable and Animal Substances. 
By W. Prout, MD. FRS. 
(To the Editor of the Annals of Philosophy.) 
DEAR SIR, Southampton-street, Nov. 15, 1822. 
In the second part of the Phil. Trans. for the present year, just 
published, there is a paper by Dr. Ure on the Ultimate ee 
of Vegetable and Animal Substances. In this paper, Dr. Ure 
states that he has constantly found about three per cent. more 
of carbon in sugar than what I obtained, and that the results of 
his analysis of urea differ very considerably from M. Berard’s 
and mine, especially in the proportion of azote. The chief object 
of this notice is to endeavour to throw some light on these dif- 
ferences ; and first with respect to sugar. Dr. Ure states that 
he employed the best refined sugar of commerce. I used per- 
fectly white and pure crystallized sugar-candy, under the im- 
pression that this would be more likely to be fixed and definite 
in its composition, than the imperfectly crystallized sugar in 
common use. I have indeed, with other views, once or twice 
operated on common sugar, but without much attention to accu- 
racy ; so that I cannot with certainty state whether my results 
coincide with those of Dr. Ure. With respect to urea, what I 
employed was perfectly pure, in which state it exists as a beau- 
