F. GEOGRAPHY. 245 



problem of sub-currents will be very difficult to solve, and 

 that it will be some time before sufficient observations can 

 be made to determine their character. There is much diffi- 

 culty in making them, since, however small the line which 

 connects the under-current drag with the float, it must be 

 acted on in some measure by the currents between the two. 



By the 1st of May the steamer reached the middle of the 

 Gulf Stream, where the temperature at the surface of the wa- 

 ter was found to be 75. On this occasion a very strong cur- 

 rent was appreciable, setting to the east -northeast, and it 

 was impossible with a line of 2600 fathoms to reach the bot- 

 tom. By experiments with the current drag it was found 

 that at 400 fathoms there was no indication of any current. 

 The influence of the Gulf Stream seemed to be expended at 

 the depth of 100 fathoms, the water there becoming rapidly 

 colder. There the stream was about sixty miles wide ; but 

 the rapid part of the current proved to be only on its western 

 edo'e, and did not exceed a breadth of fifteen miles, the rate 

 of the current being three and a half to four miles per hour. 

 The temperature of this portion of the stream exceeded that 

 elsewhere by 3. 



On this part of its course the steamer went within 120 

 miles of Long Island, and then headed for Halifax, finding 

 bottom southward of the Banks in 1200 to 1300 fathoms, 

 from which depth it rapidly shoaled toward the land. 



The Challenger reached Halifax on the 9th of May, and, aft- 

 er refitting, left on the 19th. On the 21st of May a sounding 

 was made of 1250 fathoms, and here numerous marine ani- 

 mals were brought up by the trawl and dredge. On the 22d 

 a sounding was taken close to the position of Hope Bank, 

 and a depth was found of 2020 fathoms. On the 23d, in 

 latitude 39 40' north, and longitude 63 ^' west, a tide rip- 

 ple was passed, and a diflerence of 4 in temperature was 

 found between the two sides, the colder water being on the 

 southward side. . The Gulf Stream was now entered, and a 

 sounding taken of 2000 fathoms, muddy sand. Serial tem- 

 peratures were obtained, when the warm water was found to 

 extend only 50 fathoms down. On the 26th of May sound- 

 ings were obtained in 2070 fathoms, and seven deep-sea ther- 

 mometers were lost. The trawl, at the same depth, brought 

 up a quantity of star-fishes and echini. 



