PHYTOGEOGRAPHICAL REMARKS. 481 



a year, namely in Febr.-March (the minor dry period) and in Sept.— Oct. 

 (the major dry period). Since the winds at the coast are almost without 

 exception. N. E. - • S. E., the occurrence of these maxima and minima is 

 not easy to explain. The damp north-east trade-wind, coming from the sea. 

 causes this rainfall. In the dry half-year July-Dec. the wind has a more 

 south-easterly direction, in the wet half year January— July a more north- 

 easterly. West winds are rare and generally prevail for a few hours only. 

 Since the country is flat to a very great distance from the coast, the rain 

 falls very unequally and only in local showers, except during the wet 

 period. 



About the rainfall in the interior nothing is known with certainty. It is 

 affirmed that the minor wet and dry periods are not observed there. But 

 my own observations during the months Nov.- April 1902— 1903 do- not 

 confirm this statement. The dry and wet periods which I noted during this 

 time at a distance of to 70 to 230 kilometres from the coast show exactly the 

 same data of rainfall and drought as the simultaneous observations at Para- 

 maribo. It is possible that in the month of November, when the rainfall in 

 Surinam generally increases again and the so-called minor wet period begins, 

 the showers during this month do not penetrate very far inland. This is 

 confirmed by the fact that although the month of November 1902 showed 

 at Paramaribo a rainfall far above the normal amount, yet the water in the 

 river continued to fall during the whole month. 



A marked dry period is perhaps only found in the part of Surinam, 

 situated S W. of the Wilhelmina-mountains, which range intercepts on its 

 N. E. side the rain of the sea-wind and so makes a more strongly marked 

 dry period possible for this part. 



Of the neighbouring colonies French Guyana has a climate wich resem- 

 bles that of Surinam. In Cayenne with an average yearly rainfall of 301 1 

 mm. two maxima can be distinguished, in January (361 mm.) and in May 

 (489 mm.). The minimum falls in September (28 mm.) but of a second 

 minimum nothing can be detected. At Georgetown in British Guyana with 

 an average yearly rainfall of 2138 mm. the agreement with Paramaribo is 

 greater still. Here the major maximum falls in June (303 mm), a minumum 

 in October (60 mm ), a second maximum in December (277 mm.) and a 

 second minimum in February (124 mm.) The whole littoral margin of Guyana 

 presents the same image of the rainfall under the influence of the continu- 

 ously blowing damp N. E. trade-wind The interior of British Guyana, viz. 

 the part south of 4 northern latitude and west of 59 western longitude, 

 has a long dry period through the influence of the mountains N. E. of this 

 region. The rainy period begins here in the beginning of Ma> and ends in 

 August. According to Schomburgk 1880 mm. of rain falls during this period 

 To the N. W. this region is continued into the interior country of the 

 Orinoco ; perhaps it also extends, as was remarked above, into the still 

 very incompletely known S. W. part of Surinam. But the climate of the 



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