From St. Thomas to Halifax. 67 



through Behring Strait into the Arctic basin, and eastward as 

 far as the west coast of North America. 



The isotherms of 15 C. and io° C, in the section between 

 St. Thomas and Halifax, continue to descend to a lower level 

 as the temperature of the intermediate strata increases with 

 the distance from the equator, until, at Station 52, we enter the 

 polar current. The portion of the Atlantic between Halifax 

 and Bermudas is occupied by alternate streaks of warm and 

 cold water, as will appear from the following observations 

 made on board H.M.S. " Challenger." 



After leaving Halifax on the 19th of May, the surface-tem- 

 perature marked a steady increase from 4 C, to io° C, when, 

 between 3 and 7 a.m. of the 22nd May, a rapid rise of the 

 temperature betrayed the existence of a belt of warmer water. 

 The latter attained a temperature of 17° C. between 5 and 7 p.m. 

 of the same day, but at midnight it fell to i2°.2 C, to rise half- 

 an-hour afterwards, at 12.30 a.m. of the 23rd, to 15°. 2 C. 

 Between that hour until the arrival of the ship near Bermudas 

 several alternate streaks of warm and cold water were passed 

 through, the former of a temperature from 22 to 23 C, the 

 latter from 18 to 20° C. It will be observed that the water of 

 the Gulf Stream Current was only cooled down to the extent of 

 i° C. during its passage from the section between Bermudas and 

 Sandy Hook to the section between Halifax and Bermudas. 



The centre of the first warm belt was reached at 8.30 a.m. 

 of the 23rd May, that of the second at 1 a.m. of the 24th, of the 

 third at 8 a.m., of the fourth at midnight of the same day, and of 

 the fifth at 1.30 p.m. of the 26th, the whole of the 25th May 

 having been occupied in traversing a broad belt of colder water. 

 In the vicinity of Bermudas the surface-temperature once more 

 rose to 2 3 C. 



