CHAP. VIII. ] THE GULF-STREAM. 369 
3 
glass. Currents like these must arise in all water- 
basins, and even in the oceans if different parts of 
their surface are unequally heated.” ! 
This is of course a common class-experiment illus- 
trating convection. It is evidently impossible that 
movements of ocean water can be produced in this 
way, for it is well known that everywhere, except 
under certain exceptional circumstances in the polar 
basin, the temperature of the sea decreases from the 
surface to a minimum at the bottom, and tropical 
heat is applied at the surface only. It is singular 
that this irrelevant illustration should have been 
introduced by Professor Buif; for his account of the 
origin and extension of the Gulf-stream, which may 
be taken as the type and exponent of ocean currents, 
is quite consistent with the commonly received 
opinions. 
On working up the temperature results of the 
‘ Porcupine’ expedition of 1869, Dr. Carpenter satis- 
fied himself that the mass of comparatively warm 
water, 800 fathoms deep, which we had established as 
existing, and probably moving in a north-easterly 
direction, along the west coasts of Britain and the 
Lusitanian peninsula, could not be an extension of 
the Gulf-stream, but must be due to a general cir- 
culation of the waters of the ocean comparable with 
the circulation of the atmosphere. 
«The infiuence of the Gulf-stream proper (meaning 
1 Familiar Letters on the Physics of the Earth; treating of the 
chief Movements of the Land, the Water, and the Air, and the Forces 
that give rise to them. By Henry Buff, Professor of Physics in the 
University of Giessen. Edited by A. W. Hofmann, Ph.D., F.R.S. 
London: 1851. 
BB 
