364 MEXICO, CENTEAL AMEEICA, WEST INDIES. 



A great contrast is presented by these sections : that on the north is diversified 

 with " sierras," groups of hills, and isolated eminences, one of the summits in 

 the Sierra de la Caiiada rising to a hâght of 1,540 feet ; but the sovithern section 

 is everywhere low, although the swampy savannas and impassable quagmires are 

 here and there interrupted by sharp rocks, intersected by fissures and pierced by 

 seborifcos, or pits. This part of the island seems to have been upheaved in 

 relatively recent times, for even within the historic period various islets on the 

 coast have been merged in continuous land by the mangrove thickets spreading 

 over the intervening straits and shallows. 



Similar phenomena have been observed at other points of the Cuban seaboard 

 where certain banks of dead coral, built by the same polyps that still inhabited 

 the surrounding waters, stand at present at a height of over 30 feet above sea 

 level. The hills in the neighbourhood of Havana, some of which are over 1,000 

 feet high, are certainly of coralline origin. 



Climate. 



The climate of Cuba, which lies entirely within the tropical zone, corresponds 

 to that of the neighbouring seas. Here the atmospheric phenomena present 

 great uniformity in their main features, and in this region, at the very source of 

 the Gulf Stream and of the aerial currents sweeping across the Atlantic to West 

 Europe, many of the disturbing elements of the north temperate zone may be 

 conveniently studied. 



But even in Cuba itself, which stretches across eleven degrees of the meridian 

 from the Atlantic towards Yucatan, considerable climatic contrasts have been 

 observed. Everywhere northern winds prevail, especially in winter, and every- 

 where the rains are most copious in summer, when the sun passes the zenith. 

 But as a rule the rains brought by the trade winds are more frequent and heavier 

 towards the eastern than the western extremity, on the northern than on the 

 southern seaboard. Hail is rare, though thunderstorms are common enough. 

 The rainfall is also said to have generally diminished since the destruction of the 

 forests, which has taken place especially on the central and eastern lowlands. 

 Moreover the rains, which at Havana nominally exceed 40 inches, appear to have 

 been retarded, falling regularly in June and July, instead of in April and May as 

 formerly. Even where there is no actual precipitation the air is always charged 

 with moisture, usually to an extent of over 85 per cent., and this moisture, favour- 

 ing the development of minute destructive organisms, renders the preservation 

 of archives almost impossible in such a climate. 



The whole of the island lies within the zone of hurricanes, and here the most 

 continuous and exact study has been made of these terrible disturbances. The 

 hurricane of 1846, which levelled nearly 2,000 houses in Havana, which damaged 

 more than 5,000, sank 235 vessels in the harbour and wrecked 48 others, has 

 often been referred to as a typical cyclone, though, fortunately, its track was 

 limited to a space of not more than about 20 miles. 



