CLIMATE OF GUIANA. ti.5 



winds, ft moves at scarcely more than a mile an hour, and even develops lateral 

 counter- currents and whirlpools. At such times it rises in the harbours along 

 the seaboard like a fluvial current above the weirs. 



Cjjmate of the Guianas. 



The Guianas lie entirely within the zone of the north-east trade winds. 

 Nevertheless they are sufficiently near the equator to come within the influence 

 of the prevailing south-easterlies for a part of the year. At Cayenne, which may 

 be taken as the central point of the Guiana seaboard, the normal wind, setting 

 usually from the north-east, blows regularly from the beginning of December, 

 and acquires its greatest force in January and February. At the spring equinox 

 its fury abates a little, and then follows the period of calms interrupted by 

 squalls, while in the month of July the general shifting of the atmospheric 

 currents towards the northern hemisphere is indicated by the steadily increasing 

 south-easterly breezes, Nevertheless, these south- easterlies, or rather east-south- 

 easterlies, do not blow continuously ; they prevail usually at night, being replaced 

 during the day by the land breezes. The Guiana seaboard lies entirely beyond the 

 sphere of the cyclonic storms. 



The period during which the north-easterly trade winds prevail corresponds 

 to the rainy season, which usually sets in with the normal winds, and lasts till the 

 period of irregular breezes and of the dry south-easterlies. In March the rainfall 

 is least abundant, whence the expression, "March Summer," which is applied in 

 French Guiana to this relatively dry month. But in May the moisture-bearing 

 clouds discharge their contents in cataracts, and these heavy downpours are known 

 as the Fhiies de la Foussinière, " Pleiades llains." On the Guiana seaboard the 

 mean rainfall exceeds 100 inches, and in some years the rain-gauges have 

 registered over 160 inches,* while Mr. im Thurn records a downpour of no less 

 than 13 inches in twelve hours. f 



But the precipitation varies greatly from year to year, rising at Georgetown, 

 for instance, from a little over 60 inches in 1885 to double that quantity in 1890. 

 During the rainy season the temperature is slightly lower than in summer ; 

 but it never varies more than a few degrees from the normal for the whole year, 

 which may be taken at about 80°. or 8 L° Fahr. In the interior, the range between 

 the extremes is slight, thanks to the uniform relief of the land, which presents 

 no great elevations except in the Pacaraima uplands. But the greatest differences 

 are observed in the distribution of moisture. Thus the rain-beuring clouds 

 intercepted by the mountains discharge their contents in torrents on the higher 

 summits, whereas they part with but little of their humidity on the plains, where 

 they meet with no obstacles. 



But even here the atmosphere is nearly always charged with a large quantity 

 of aqueous vapour. At dusk the fogs spread like a vast shroud over the wood- 

 lands, where they are often pierced by the large trees, whose crests rise above the 



* Rainfall of Cayenne in 1874 : 168 inches (Maurel and Hardy), 

 t Journal of the Culonial Ins-titute, 1892 — 93. 



