815 



latitudes, when made at a time when the wind 

 does not blow from the north, and when the cur- 

 rents are less violent. The north-winds and the 

 currents cool the water by degrees, even where 

 the sea is very deep. On the south of cape Co- 

 rientes, lat. 20 o 43', I found the sea at its sur- 

 face 24.6°, and the air 19.8° cent. Some Ame- 

 rican pilots affirm, that among the Bahama 

 Islands they can often guess, when seated in 

 the cabin, that they are passing over sand- 

 banks ; they pretend that the lights are sur- 

 rounded with small coloured halos, and that 

 the air breathed is condensed in a visible man- 

 ner. It may be permitted to doubt at least 

 the latter fact ; below 30° of latitude the cool- 

 ing produced by the waters of the banks is not 

 sufficiently considerable to cause this pheno- 

 menon. During the time we passed on the 

 bank of the Vibora, the constitution of the air 

 was quite different from what we found on 

 quitting it. The rain was circumscribed by 

 the limits of the bank, of which we could dis- 

 tinguish the form from afar, by the mass of va- 

 pors with which it was covered. 



December 9th. — As we advanced towards the 

 islands of the Caymans *, the north-east wind 



* Christopher Columbus, in 1503, named the islands of 

 the Caymans, Penascales de las T ortugas, on account of the 

 sea-tortoises which he saw swimming in those latitudes 

 (Herera, Decad., i, p. 140). 



