154 



humboldt's ctjba. 



It seldom happens in winter that the temperature 

 falls to 10° or 12° 0. (50° to 53°.6 F.), but when the 

 north wind prevails for several weeks, bringing the 

 cold air of Canada, ice is sometimes formed at night, 

 in the interior of the island, and in the plain near 

 Havana. From the observations of Messrs. Wells 

 and Wilson, we may suppose that this effect is 

 produced by the radiation of caloric when the 

 thermometer stands at 5° 0. (41° F.), and even 9° 0. 

 (48°.2 F.) above zero. This formation of a thick ice 

 very near the level of the sea, is more worthy the 

 attention of naturalists from the fact, that at 

 Caraccas (10° 31/ N. lat.), at an elevation of 300 

 feet, the temperature of the atmosphere has never 

 fallen below 11° C. (41°.8 F.) ; and that yet nearer 

 to the equator we have to ascend 8,900 feet to see ice 

 form. We also observe that between Havana and 

 St. Domingo, and between Batabano and Jamaica, 

 there is a difference of only 4° or 5° of latitude, and 

 yet, in St. Domingo, Jamaica, Martinique, and 

 Guadalupe, the minimum temperature in the plains 

 is from 18°.5 to 20°.5 O. (65°.3 to 68°.9 F.) 



It will be interesting to compare the climate of Ha- 

 vana with that of Macao and Rio de Janeiro, one simi- 

 larly situated near the northern extreme of the torrid 

 zone, but on the eastern shore of Asia, and the other 

 near the southern limit of the torrid zone, on the 



