ae On the Gulf Stream and the Keys of Florida. 59 
Now, these ridges and hollows may be conceived to have been 
formed in either of two ways, viz.: by igneous or current agency. 
upon land valleys are formed either by igneous or aqueous 
agency, 2.¢. may be valleys of elevation or valleys of erosion ; 
So also in the sea, ridges may be formed by igneous or current 
agency, 7. ¢., may be ridges of elevation or ridges of deposit. In 
either case there would be conformity between the direction of 
the ridges and the direction of the current, only in the one case 
the current would conform to the ridges, and in the other the 
ridges would conform to the current. 
n order to account for these ridges by this current theory, the 
tic Water, and the resulting ridges.would therefore continue for 
Steat distances. I know not whether there have been any obser- 
vations to test the comparative velocity of the warm and 
bands, but it seems to me that on any conceivable theory as to 
jhe formation of the ridges the velocity of the cool bands would 
ess. 
Now, though it may be impossible in the 
Sclence to deine as absolute certainty whether these i 
