254 THREE CRUISES OF THE " BLAKE." 



Commander Bartlett found no warm or cold bands, no distinct 

 cold wall, and no bifurcations in the surface waters till be came 

 off Hatteras. Near the shore, the current was greatly influ- 

 enced by winds. The work of the " Blake " seems to show 

 that the cold bands so called, which figure so largely in all early 

 descriptions of the Gulf Stream, have no regularity, and only 

 represent at any given moment the unceasing conflict going on 

 between layers of water of different velocities and of different 

 temperatures. Such a conflict is perhaps the well-known rip we 

 encountered off Charleston, which may be caused by a struggle 

 between portions of the Labrador current passing under the 

 Gulf Stream. As the isotherms rise and fall with the irregu- 

 larities of the bottom, where water accumulates or piles against 

 ridges, hot and cold bands may be flowing one above the other. 

 We need, however, more prolonged observations to show how 

 far below the surface these bands extend. Commander Bartlett 

 from the last Coast Survey investigations under his direction 

 is inclined to consider the cold bands of the Gulf Stream as 

 quite superficial.^ 



A cold current striking against a warmer stream that is flow- 

 ing in the opposite direction may split it into more or less 

 marked hot and cold bands. Bands similar to those of the 

 Gulf Stream were observed by the " Challenger " in the Agu- 

 Ihas current off the Cape of Good Hope, and off Japan in the 

 Kuro-Siwo. 



It is of course difficult to ascertain the part taken by the 



we must not forget to add to it that of mudas, Sir Wyville Thomson speaks of 



the greater mass of heated water which passing alternate belts of cold and warm 



is forced north, and finds its way to the water. Early in the morning of the 22d 



northernmost shores of Siberia, losing in of May, the surface water was of a tem- 



its passage the heat it has accumulated perature of 17° C. ; at midnight it had 



\vithin the tropics. So that, while we fallen to 12° C, to rise again half an 



cannot say that the Gulf Stream has dis- hour later to over 15° C. Thus, from 



appeared, and has been replaced oft" the the time the " Challenger " left Hali- 



Banks of Newfoundland by the equato- fax with a surface temperature of 4° 



rial drift, neither can we attribute to the C, gradually rising to 10° C. until she 



Atlantic drift alone the masses of warm encountered the Gulf Stream proper, 



water found in the basin of the northern marked by a rapid rise of temperature, 



part of the North Atlantic. (See Figs, she passed through alternate belts of 



170 and 175.) warm and cooler surface waters varying 



1 In sailing from Halifax to the Ber- between 18° C. and 23° C. 



