CHAP. 111.] THE GULF-STREAM. Baal 
local accidents as those which produce the Gulf- 
stream proper, and which gives movement to a much 
larger and deeper body of water than the latter can 
affect. The evidence of such an interchange is two- 
fold—that of physical theory, and that of actual 
observation. Such a movement must take place, as 
was long since pointed out by Professor Buff, when- 
ever an extended body of water is heated at one part 
and cooled at another; it is made use of in the warm- 
ing of buildings by the hot-water apparatus, and it 
was admirably displayed at the Royal Institution a 
few months since in the following experiment kindly 
prepared for me by Dr. Odling.” Dr. Carpenter 
then repeats Professor Buff’s convection experiment, 
the heat being applied by a steam jet introduced 
vertically at one end of a narrow glass trough while 
a block of ice was wedged into the other end 
“Thus a circulation was shown to be maintained in 
the trough by the applcation of heat at one of its 
extremities and of cold at the other, the heated water 
flowing along the surface from the warm to the cold 
end, and the cooled water flowing along the bottom 
from the cold to the warm end; just as it has been 
maintained that equatorial water streams on the 
surface towards the poles, and that polar water 
returns along the bottom towards the equator, if 
the movement be not interfered with by interposed 
obstacles, or prevented by antagonistic currents 
arising from local peculiarities.’’! 
That such a movement cannot take place on this 
hypothesis has been already shown; and Dr. Car- 
1 The Gulfstream. A letter from Dr. Carpenter to the Editor of 
Nature, dated Gibraltar, August llth, 1870. (Nature, vol. ii. p. 334.) 
BB. 2 
