Chemistry and Physics. 119 
ed with waxed glass having designs on it. The latter were etched in 
two hours, as deeply as they could have been by fluor-spar treated in 
thé same way, the lines being filled up with the white silica, separated 
from the glass. The author has recently examined in the same wa 
bittern from the salt-works at Saltcoats, in the Firth of Clyde, but the 
indications 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 
wax. A sin 
slightly, but by replenishing the basin with successive quantities of these 
materials, whilst the same plate of engraved glass was used as the cover, 
are periodically removed from the boilers of the ocean steame 
t of the sea. He made application, accordingly, at Glasgow and 
Leith for the deposits in question. It appears, however, that the deep- 
Sea steamers which leave the former have their boilers cleaned out at 
other ports, so that he has as yet been unsuccessful in procuring crusts 
from the west coast of Scotland. He has obtained at Leith the crust 
once yielded hydrofluoric acid. A single charge, indeed, of the mate- 
rials marked the glass distinctly, and four charges deeply. We may 
tained fluorine pretty equally diffused through it. From what is known 
of the comparative uniformity in composition of sea-water, it may safely 
