308 THE ATLANTIC. [chap. v. 



unwise to attempt to draw any general conclusions from such 

 imperfect data. Considering, however, our four parallel sec- 

 tions, we have at least this positive result — that in the month 

 of Jnne and mean lat. 36° N. the surface-water in mid-ocean 

 has a mean specific gravity of 1'02712; tliat in the months 

 of February and March and mean lat. 22° N. the mean surface 

 specific gravity is 1*02773 ; that in the month of August and 

 mean lat. 2° I^. it is 1-0262-i ; and that in the month of October 

 in mean lat. 36' S. it is 1-02621. 



On the way to and from Halifax, in the month of May, some 

 observations were obtained in the cold water with which the 

 north-eastern coast of America is surrounded, the mean specific 

 gravity being 1-02463. On the 1st of May, in the Gulf-stream, 

 the specific gravity of the water was 1-02675, and its tempera- 

 ture 23°-9 C. ; and the next day it was 1-02538, and the temper- 

 ature 13°-3 C. If the results be reduced to their values at the 

 respective temperatures of the difi^erent waters, we have for the 

 specific gravity of the Gulf-stream water 1-02145, and of Labra- 

 dor-current water 1-02584 ; so tliat the fall of temperature very 

 much more than counterbalances the want of salt in the water. 

 In the same way we find the mean specific gravity of the water 

 referred to the temperature which it has in the ocean to be, in 

 lat. 36° N. and month of June, 1-02548 ; in 22° N. and months 

 of February and March, 1-02592 ; in 2° N. and month of Au- 

 gust, 1-02335 ; and in 36° S. and month of October, 1-02659. 



From the determination of the specific gravity of intermedi- 

 ate and bottom water, Mr. Buclianan concludes that, as a gener- 

 al rule, both in the Atlantic and the Pacific oceans, between the 

 parallels of 40° IST. and 40° S., the specific gravity reduced to 

 15-56 C, is greatest at or near the surface, and decreases more 

 or less regularly until a minimum is reached, generally 400 fath- 

 oms from the surface, whence there is a slow rise, the bottom- 

 water being slightly heavier. 



From Mr. Buchanan's report, and from the specific -gravity 



