OF SEA-WATER IN THE DIFFERENT PARTS OF THE OCEAN. 
209 
other salts that occur in sea-water, in the beds of rock-salt at Stassfurth in Germany. 
The lower part of this bed of rock-salt, which by a boring was not penetrated through 
at a depth of 800 feet, consists of pure chloride of sodium. Upon this rest the other 
salts of sea-water, consisting of magnesia, lime, and potash combined with muriatic and 
sulphuric acids in numerous combinations, among which we also find the Stassfurthite 
(borate of magnesia with chloride of magnesium). Boracite, a similar combination of 
boracic acid, occurs at Luneburg and at Segeberg, associated with gypsum and chloride 
of sodium, which latter at Luneburg forms a spring of saturated brine, and at Segeberg 
occurs in separate crystals imbedded in the gypsum. 
I thought I might be able to form a borate insoluble in water, and with such charac- 
teristic properties that it might be possible to determine the boracic acid in it. It is 
well known that Heintz, by melting chloride of magnesium, chloride of sodium, mag- 
nesia, and boracic acid, obtained octohedral crystals, which were boracite, and another 
set of crystals, of hemiprismatic form, which also contained boracic acid and magnesia. 
The crystals were microscopic, but could easily be recognized by their different form of 
crystallization. To make myself acquainted with these different artificial combinations, 
I melted borax, common salt, and sulphate of magnesia in a crucible, allowed it to cool 
slowly, and dissolved it in water. There remained a heavy crystalline powder, which 
under the microscope proved to consist of six-sided hemiprismatic prisms, containing 
both magnesia and boracic acid. I could not discover any octohedral crystal, and no 
boracite seemed to have been formed. In another experiment I fused common salt, 
magnesia, and borax; after solution I obtained the same hemiprismatic crystals, but 
no octohedrons ; and felt now convinced that I hardly should obtain boracite by fusing 
salt of sea-water, but that I might obtain the hemiprismatic borate if sea-water con- 
tained boracic acid. 
The experiment was made in the following way : — I evaporated 6 lbs. of sea-water 
taken from the Sound near Copenhagen, transferred the salt into a perfectly clean 
platinum crucible, which was placed upon magnesia in a common Hessian crucible, 
exposed it to a white heat, and cooled slowly. After solution of the salt, the powder 
remaining was placed under the microscope, where it was found to consist almost 
entirely of hemiprismatic crystals which frequently formed twins* and by their whole 
exterior showed themselves to be essentially different from the hemiprismatic borate. 
Many of them were corroded at the sides and ends, as if they had partly been dissolved. 
I supposed them to be gypsum, which of course must be formed by the evaporation of 
sea-water ; and although the gypsum by melting would be changed into anhydrite, they 
afterwards, during washing with water, would again form a hydrate. I thought even 
several times to have seen square prisms (anhydrite'?) change into the hemiprismatic 
form under my observation in the microscope, and get oblique cracks like one cleavage 
of gypsum. The powder was again washed with hot water, and the solution was 
found to contain both sulphuric acid and lime. When the wash-water contained 
only traces of sulphuric acid, the powder, greatly diminished in quantity, was again 
