160 On the Theory of Marine Currents. 
and Kyanite are also identical ; the one being derived by the simplest 
modification from the other. The cleavage in both is in the ortho- 
diagonal. 
It may be worthy of remark, that ‘‘ Andalusite’’ has the same che- 
mical constitution as Kyanite, but belongs to the right rhombic form, 
while Kyanite is oblique, doubtless a case of dimorphism, and, per- 
haps, the same may be said with truth of stanrotide. My pupil, Mr 
George J. Brush, afforded me essential aid in the foregoing investi- 
gation.—(Silliman’s Journal, vol. viii., No. 24. 2d series, p. 
386.) 
Theory of Marine Currents. By M. BABINET. 
The theory of the movement of the waters in the different 
oceans which cover the greater part of our globe, does not 
hitherto appear to have been placed, like that of the trade- 
winds and their counter-currents, on the rigorous principles 
of mechanics and physics. In order to compare theory with 
facts, 1 shall confine myself exclusively to M. Duperrey’s 
Map of the general and permanent currents of seas, inde- 
pendently of the superficial and temporary currents produced 
every season by the prevailing winds in a great number of 
maritime localities. This map has been constructed from 
facts observed by the author himself, and by other navigators 
engaged in scientific investigations, without regard to any 
theory. It presents us, therefore, with the laws to which 
every theory ought to conform ; and, on the other hand, every 
theory which shall reproduce these facts in all their details, 
will, to a certain extent, derive support from it. 
It is a notion of the French school of Laplace, already in 
possession of the public, that the semidiurnal swellings of 
the sea, called tides, which are produced successively from 
east to west (affording us the measure of the mean depth of 
the different oceanic basins), cannot give rise to any current 
in the fluid masses of the earth’s surface.* 
The current of the Gulf Stream, or, to speak more accu- 
rately, the circulation of the waters of which the Gulf Stream 
forms a part, has been recently ascribed by M. Maury to a 
* Not a circulating current. John Herschel, 1833 and 1849. 
