352 THE CAYMAN ISLANDS 



that we were on the eastern part of the bank ; the centi- 

 grade thermometer, which at a distance from the bank, and 

 on the surface of the sea, had for several days, kept at 27* 

 and 27-3 (the air being at 212), sank suddenly to 25*7. 

 The weather was bad from the 4th to the 6th of December : 

 it rained fast ; thunder rolled at a distance, and the gusts of 

 wind from the N.N.E. became more and more violent. We 

 were during some part of the night in a critical position ; we 

 heard before us the noise of the breakers over which we had to 

 pass, and we could ascertain their direction by the phosphoric 

 gleam reflected from the foam of the sea. The scene resem- 

 bled the Eaudal of Garzita, and other rapids which we had 

 seen in the bed of the Orinoco. "We succeeded in changing 

 our course, and in less than a quarter of an hour were out of 

 danger. While we traversed the bank of the Vibora, from 

 S.S.E. to N.N.W., I repeatedly tried to ascertain the tem- 

 perature of the water on the surface of the sea. The cooling 

 was less sensible on the middle of the bank than on its 

 edge, a circumstance which we attributed to the currents 

 that there mingle waters from different latitudes. On the 

 south of Pedro Keys, the surface of the sea, at twenty-five 

 fathoms deep, was 26'4 and at fifteen fathoms deep 26 - 2. 

 The temperature of the sea on the east of the bank had 

 been. 26'8. Some American pilots affirm, that among the 

 Bahama Islands they often know, when seated in the cabin, 

 that they are passing over sand-banks ; they allege that 

 the lights are surrounded with small coloured halos, and 

 that the air exhaled from the lungs is visibly condensed. 

 The latter circumstance appears very doubtful ; below 30 

 of latitude the cooling produced by the waters of the bank 

 is not sufficiently considerable to cause this phenomenon. 

 During the time we passed on the bank of the Vibora, the 

 constitution of the air was quite different from what it had 

 been when we quitted it. The rain was circumscribed by the 

 limits of the bank, of which we could distinguish the form 

 from afar, by the mass of vapour with which it was covered. 

 On the 9th of December, as we advanced towards the 

 Cayman Islands,* the north-east wind again blew with 



* Christopher Columbus, in 1503, named the Cayman Islands " Penas. 

 cales de las Tortugas," on account of the sea-tortoises which he W9 

 swimming in those latitudes* 



