152 
THE CATMAIT ISLANDS 
^“’^5 the cent;- 
nr„i *97 qo’’^fL® °ft|*'’,®®s> for several days, kept at 27" 
.^ d2/3 (the air being at 21 2°), sank suddenly to 25-7‘>. 
Ihe 11 Gather was bad from the 4th to the Gth of December: 
’ tliujider rolled at a distance, and the gusts of 
fiom the Iv .N.E. became more and more liolenL ^Ve 
Wdtf"® “‘S’** “ critical position ; ive 
hea, d before us the noise of the breakers over ivl/ich ive had to 
pass, and we could ascertain their direction by the phosiilioric 
b ed’?hjJ 1 1 ® f *’‘® '■i'l’CscLe resem- 
? 11 ^ f^^**^***^’ ‘'inc* other rapids which wc liad 
seen in the bed of the Orinoco. We succeeded in chnn<ri„cr 
our eourse^and in less than a quarter of an hour were out of 
*‘'’i^oi‘sod the bank of tlie Vibora, from 
■b.fi.E. to N ^.W., I repeatedly tried to ascertain the tem- 
peratoe of the water on the surface of the sea. Tlie cooling 
^^^^s less sensible on the middle of the bank than on its 
Tliftw''''-™! we attributed to the currents 
S: th orp’T"® !® from different latitudes. Ou the 
south of Pedro Keys, the surface of the sea, at tweiitv-five 
frthoms deep was 20-4“ and at fifteen fathoms deep 26'2h 
him, ®‘‘®* bank had 
Deen ^(> 8 home 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 
tliat the air e.xbaled from the lungs is visibly condensed. 
;]*? !?**7 circumsteiice appears very doubtful; below 30“ 
of latitude the cooling produced by the waters of the bank 
m not sufficiently considerable to cause this phenomenon. 
During the tniie we passed on the bank of the Vibora, the 
constitution of the air was quite different from what it had 
circumscribed by the 
limits of the bank, of which we could distinguish the form 
from afar, by the mass of vapour with wliich it was covered. 
On the 9th of December, as wo advanced towards the 
Cayman Islands,* the north-east wind again blew with 
* Christoj.her Columbus, in 1503, named tlie Cayman Islands '■ Penas- 
cales de las Tortups, on account of the aea-tortoiscs which he saw 
swimming in those latituiles. 
