( 345°) 
On the proportion of Fluoride of Calcium present in the Baltic. 
By Professor FORCHAMMER of Copenhagen. With some 
Preliminary Remarks on the presence of Fluorine in differ- 
ent Ocean Waters. By Dr GEORGE WILSON, F.R.S.E.* 
Communicated by the Author. 
In 1846, I announced the discovery to the Royal Society 
of Edinburgh of fluorine as a new element of sea-water. I 
was led to search for it, after observing that fluoride of cal- 
cium possesses a certain small but marked solubility in water, 
which explains its occurrence in springs and rivers, and ne- 
cessitates its occasional, if not constant presence in the sea. 
The only specimens of sea-water I had examined before 
last summer, were taken from the Frith of Forth, about three 
miles from Edinburgh. I obtained the mother-liquor or 
bittern, from the pans of a salt-work there, and precipitated 
it by nitrate of baryta. The precipitate, after being washed 
and dried, was warmed with oil of vitriol, in a lead basin, 
covered with waxed glass with designs on it. The latter were 
etched in two hours, as deeply as they could have been by 
fluor-spar, treated in the same way, the lines being filled with 
the white silica, separated from the glass. 
Last summer | examined in the same way bittern from the 
salt-works at Saltcoats, in the Frith of Clyde, but the indi- 
cations of fluorine were much less distinct than in the waters 
on the east coast. On procuring, however, from the same 
place, the hard crust which collects at the bottom and sides 
of the boilers used in the evaporation of sea-water at the salt- 
works, I found no difficulty in detecting fluorine in the de- 
posit. The crust, or deposit in question, consists in greater 
part of sulphate of lime, and of carbonate of lime, and mag- 
nesia, but it contains also much chloride of sodium, and the 
other soluble salts of sea-water,.entangled in, its substance. 
When sulphuric acid, accordingly, is poured upon it, it gives 
off much hydrochloric and carbonic, as well as some hydro- 
* Read before the Royal Society of Edinburgh, 4th March 1850, 
