202 THE GULF STREAM, 
Commander Bartlett found no warm or cold bands, no distinet cold 
wall, and no bifureations in the surface waters till he came off Hatteras, 
Near the shore the current was greatly influenced by winds. The 
work of the Blake seems to show thatthe cold bands, so called, which 
figure so largely in all early descriptions of the Gulf Stream, hes eno 
regularity, and only represent at any given moment the unceasing con- 
flict going on between layers of water of different velocities and of dif- 
ferent temperatures. Such a conflict is perhaps the well-known rip 
we encountered off Charleston, which may be caused by a struggle be- 
tween portions of the Labrador current passing under the Gulf Stream. 
As the isotherms rise and fall with the irregularities 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 pro- 
longed observations to show how far below the surface these bands 
extend. Commander Bartlett, from the last Coast Survey investiga- 
tions 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 flowing 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 Agulhas 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 trade-winds 
in originating the oceanic circulation of the Atlantic. That winds 
blowing steadily from one quarter give rise to powerful currents is 
well known, and it is not difficult to imagine the prominent part the 
trades must play in setting in motion, in a southwesterly and anorth- 
westerly direction, the mass of water over which they sweep so persist- 
ently on each side of the equator. 
The change of currents in the Indian Ocean due to the shifting of 
the monsoons is well known. How far below the surface this action of 
the winds reaches, is another question.t Theoretically it has been cal- 
culated by Zoeppritz that one hundred thousand years is ample time to 
allow the friction of the aie sy to extend from the surface to the bot- 
“Th Seine om Halifax to ine Bae aS Ww Vv Ae Thowcon ES. of passing 
alternate belts of cold and warm water. Early in the morning of the 22d of May, 
the surface water was of a temperature of 17° C.; at midnight it had fallen to 12° 
C., to rise again half an hour later to over 15° C. Thus, from the time the Challen- 
ger left Halifax with a surface temperature of 4° C., gradually rising to 10° C. until 
she encountered the Gulf Stream proper, marked by a rapid rise of temperature, she 
passed through alternate belts of warm and cooler surface waters varying between 
18° C. and 23° C. 
t The movement arising from the action of the winds on the surface is transmitted 
by friction from one layer to another and communicates the velocity of the upper 
particles to the underlying layers in succession. If this is continued long enough, 
the velocity of the lowest layers will equal within a fraction that of the upper layer. 
