792 POPULAR SCIENCE MONTHLY. 



and mountainward tourists need their water boots in every glen; 

 the gnat veil of ordinary years has thickened to heavy banks of gnat 

 clouds, and the nights are made ghastly by the serenades of renegade 

 tomcats that have exchanged the shelter of their native ranches for 

 the freedom of the woods, but have to wait for the cloud-dispelling 

 moon to celebrate their declaration of independence. 



The supposed rain-attracting excess of heat has, however, nothing 

 to do with the intervention of rainy summers. In the western prov- 

 inces, where rain is often sorely needed, they are rare — much rarer, 

 at least, than in the wood-covered southeast. Their recurrence seems 

 somewhat to depend upon the above-mentioned cold-air waves from 

 the woodlands of Central America, cool weather in June having a 

 tendency to postpone the beginning of the rainy season and to in- 

 crease the vehemence of the eventual downpour. In other words, the 

 early showers of Yucatan and of the West Indian Islands are apt to 

 occur in alternate years, but there are summers when cloud bursts 

 break out without any other premonition but the steadily increasing 

 sultriness of the weather during the latter half of July. 



Hurricanes are still harder to predict. Experience has proved 

 that they are generally more frequent in Santo Domingo and Porto 

 Rico than in the western Antilles, but the occasional destructiveness 

 of their rage in Cuba is attested by numerous cadenzas, or tracts of 

 leveled forest lands, from Santiago to Pinar del Rio, and their genesis 

 is still rather obscure. As a rule, the equalization of extreme con- 

 trasts of temperature is attended with violent gales, and in early 

 spring northwest storms, traversing the mainland from Hudson Bay 

 Territory to southern Texas, may approach the threshold of the 

 tropics nearly a hundred degrees cooler than the atmosphere brooding 

 over the coast plains of San Salvador, where pears begin to ripen in 

 April. And the fortnight following the vernal equinox is really a 

 season of shipwrecking gales, in east America as well as in western 

 Europe and the Asiatic coast lands of the North Pacific. But the 

 tornadoes proper, the wall-breaking and tree-uprooting whirl storms 

 of the West Indies, are more frequent in August than in April, and 

 may even assume their most portentous forms in September, when 

 the summer sun at last prevails against the mists of the rainy season, 

 and the vegas are some twenty or thirty degrees warmer than the 

 Texas prairies — a mere trifle compared with the contrasts of early 

 spring. 



Moisture would seem to play almost as important a part as heat 

 in the generation of cyclones, and Professor von Tschudi called atten- 

 tion to the fact that the dry if not wholly rainless coast regions of 

 Peru enjoy a remarkable immunity from destructive storms. 



Cold winds become afflictive only on the highest plateaus of the 



