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On the Depth and Saltness of the Ocean. 45 
the day, from early in the morning till late in the evening, the 
altitude of the sun being measured at each trial. These experi 
ments took place when the sea was nearly calm and quite smooth ; 
the greatest depth at which the object could be perceived, was 
30 fathoms, or 180 feet: 
_ The next phenomenon connected with the depth of the ocean 
iS submarine currents; they exist in various parts of the ccean 
where they have been traced, and are indicated by their low tem- 
perature ; their actual limits as to depth have not as yet been de- 
termined, but they are found to prevail at from 5 to 600 feet be- 
low the surface ; they are so immediately connected with the 
dynamics of the ocean, that the investigation into their direction 
and causes has long obtained attention. 
- The saltness and specific gravity of the sea have been frequent 
_ Subjects of enquiry. The results of the Expedition will throw 
much light wpon this subject. The specimens of sea-water ob- 
tained in different latitudes were, on the return of the Expedition, 
placed in the hands of one of our most distinguished associates, 
‘Dr. C. T. Jackson of Boston, whose ability as a chemist is well 
known to the country ; he has analyzed them, and as it will yet 
be some time before the full results can be published in the 
volumes of the Expedition, the Association will be gratified by 
a knowledge of his method of analyzing, as well as by a few of 
e results, 
- Method of Analysis.—“ The specific gravity of the waters was 
taken in a small flask with a neck of about } inch in diameter. 
A quantity of the water equal to 1000 grains of distilled water, was 
evaporated slowly to dryness in a platina capsule, carrying the 
heat to 300° F., then weighed the contents by counterpoising. 
