118 Mr Middleton on Fluorine in Recent and Fossil Bones. 
stances :—First, A deposit, chiefly of sulphate of lime, from 
as it appeared, a chloride of calcium vat, and found it to con- 
tain fluorine, though in small quantity. As it was suggested 
to me, however, that glass retorts, used for the distillation 
of hydrochloric acid has been known to be thereby corroded, 
I did not attach much weight to the result, although I drew 
encouragement from it. 
Second, A deposit, formed in a wooden conduit pipe in a 
coal mine, procured for me by my friend Dr Falconer, and 
found it to contain a still greater proportion of fluorine than 
the former. : 
Third, A stalactitie deposit, said to have been formed in 
an aqueduct in France. It was of a pure white colour, and 
made up of very thin and scaly concentric layers, being at 
the same time very incompact ; it contained no fluorine. 
Fourth, A stalactitic deposit from a cave in old red sand- 
stone, furnished to me by Mr Arnott, to whom, for this and 
for other assistance in my investigations, I am much indebted. 
This I found to contain fluoride of calcium to the extent of 
about 9 per cent. The stalactite consisted chiefly of car- 
bonate of lime. 
Fifth, The crust formed on the inside of a. kettle used for 
the boiling of water. This I found to afford faint but distinct 
proof of the presence of fluorine. 
Lastly, A fragment of a vein of sulphate of barytes, found 
in the sandstone above mentioned. This also contained fluo- 
rine, though in much less proportion than the stalactite of the 
fourth experiment. 
The above are the only substances, sufficiently diverse in 
their origin, which I have had an opportunity of examining ; 
and the facts I have elicited from them seem to confirm the 
justness of my theory of the prime sources of fluorine in 
bones. It follows, as a necessary corollary, that it exists in 
most, if not all vegetables, though perhaps in minuteness of 
quantity, that may enable it often to elude detection —( Philo- 
sophical Magazine. Third Series, Vol. xxy., No. 166, p. 260.) 
