CHAP, vin.] THE GULF-STREAM. 369 



glass. Currents like these must arise in all water- 

 basins, and even in tlie 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 i'rom 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 Buff; 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 circu- 

 lation of the w^aters of the ocean comparable with 

 the circulation of the atmosphere. 



" The influence of the Gulf-stream proper (meaning 



^ FamOiar 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: 185L 



