48 REPORT—1849. 
a waxed square of plate-glass, with letters traced through the wax. A single charge 
of the crust and acid corroded the glass only slightly ; but by replenishing the basin 
with successive quantities of these materials, whilst the same plate of engraved glass 
was used as the cover, he found no difficulty in etching the glass deeply. The author 
is indebted to his friend Mr. S. Macadam for this simple but effective way of in- 
creasing the corrosion of the glass, which seems worth the adoption of chemists in 
all cases where fluorine is sought for. Four charges of material have been sufficient, 
with all the specimens of sea-water deposit he has examined, to mark the glass 
strongly. It was kept wet on the upper side, and exposed undisturbed to the action 
of each charge during twelve hours. Operating in this way, he has found fluorine 
readily in the beiler-deposit from the waters of the Firths of Forth and Clyde. It 
is a less easy matter to subject the waters of the open sea to the requisite concen- 
tration before examination. It occurred to the author, however, that the incrusta- 
tions which are periodically removed from the boilers of the ocean steamers would 
serve to determine the question whether fluorine is a general constituent of the sea. 
He made application, accordingly, at Glasgow and Leith for the deposits in question. 
Tt appears, however, that the deep-sea steamers which leave the former have their 
beilers cleaned out at other ports, so that he has as yet been unsuccessful in pro- 
curing crusts from the west coast of Scotland. He has obtained at Leith the crust 
from the boiler of a steamer called the ‘St. Kiaran*,” which trades between that port 
and Montrose; so that the greater part of the water consumed as steam by its en- 
gines is derived from the German Ocean, although a portion is necessarily obtained 
from the Firth of Forth. The crust from the boilers of this vessel was treated in the 
way described, and at once yielded hydrofluoric acid. A single charge, indeed, of 
the materials marked the glass distinctly, and four charges deeply. We may there- 
fore infer that fluorine is present in the waters of the German Ocean, for different 
portions of the deposit yielded it readily, and marked glass as deeply as the deposit 
from the water of the Firth of Forth did, which could not have been the case if the 
whole crust had not contained fluorine pretty equally diffused through it. 
It will be an interesting matter to have similar examinations made of the boiler 
deposits from the Transatlantic, and other ocean steamers which make long voyages; 
nor will it be difficult, where the crust is thick, to select portions from the interior 
of the deposit, which may be regarded as best representing the contents of the sea 
at a considerable distance from land. From what is known of the comparative uni- 
formity in composition of sea water, it may safely be inferred that if fluorine be 
present in the waters of the Firths of Forth and Clyde and in the German Ocean, it 
will be found universally present in the sea. In one of the interesting communica- 
tions which Prof. Forchhammer has laid before the British Association, he has shown 
that the more marked ingredients of sea water vary little over wide areas. One of 
the ingredients selected by this gentleman to mark the uniformity in composition of 
the sea, is lime, and as it is exceedingly probable that the fluorine in sea water exists 
in the state of fluoride of calcium, his observations may be referred to as in harmony 
with the inference that the element in question is generally diffused through the sea. 
Other proofs, however, are not wanting. Mr. Middleton, before 1846, came to the 
conclusion that fluorine must be present in sea water, since it occurred, as he had 
ascertained, in the shells of marine mollusca, Silliman, jun., without a knowledge 
of Middleton’s views, drew the same inference, from its invariable presence in the 
calcareous corals brought to America by the United States’ expedition from the Ant- 
arctic seas. ‘The author has found fluorine abundantly present in the teeth of the 
walrus, which points to its existence in the Arctic Ocean; and it seems so invariably 
to associate itself with phosphate of lime, that it may be expected to occur in the 
bones of all animals marine and terrestrial. 
The author has found fluorine likewise in kelp from the Shetlands, but much less 
distinctly than he anticipated. Glass plates were only corroded so far as to show 
marks when breathed upon. Prof. Veelcker also was kind enough, at the author’s 
request, to search for fluorine, when analysing the ashes of specimens of the sea pink 
* In the account of this paper contained in the Atheneum report of the meeting of the 
British Association for 1849, the name of the vessel was inadvertently called the ‘ Isabella 
Napier ’ instead of the ‘St. Kiaran.’ They both traded between Leith and the northern 
parts of Scotland, 

