652 



NATURALIST'S GUIDE TO THE AMERICAS 



Sunshine. The average daily sun- 

 shine is 5.3 hours the greatest amount 

 being felt in September (6.8 hours) and 

 October (6.7 hours) followed closely by 

 November (6.3 hours) and August 

 (6.2 hours). May (4 hours) followed by 

 March (4.3 hours) have the least sun- 

 shine. The maximum amount of sun- 

 shine recorded for a single day is 11.6 

 hours. 



Temperature. Seventy-nine and two- 

 tenths degrees is the average shade tem- 

 perature for the year, the highest tem- 

 perature being in October (81.5) and 

 September (81.1), and the lowest in 

 January (77.8). The maximum and 

 minimum temperatures for the year 

 average as follows : 



Maximum 83 .9 



Minimum 74.3 



The following list will show the 

 grouping of the months, the coolest 

 month placed first and the warmest 

 last: January, February, March, June, 

 July, December, April, May, August, 

 November, September, October. 



Winds. The winds at Kartabo vary 

 from "gentle" to "fresh" and average 

 3.5 mi. per hour. Because of Kartabo's 

 position the trade winds blow almost 

 steadily throughout the year, while in 

 January, February and March, they 

 continue through much of the night 

 as well. 



Meteorology of Kartabo compared with 

 the Coast of Guiana and with the far 

 interior. The following table will show 

 the variation in rainfall, humidity and 

 temperature between the coast as 

 represented by the records taken at 

 Georgetown, and the far interior as 

 represented by the re-cords taken at 

 Dada-nawa, far up on the savannas. 

 The interior station shows a far greater 

 range of temperature and rainfall 

 than do either of the other two places. 



Physical features 



Land mass. The average height of 

 the land mass at Kartabo is between 

 40 and 50 ft. above the mean high tides. 

 Along the shore of the Mazaruni im- 

 mediately in front of the Station the 

 land is from 5 to 15 ft. above the river. 

 In back of the laboratory the land rises 

 sharply at first, forming a rounded hill 

 about 80 ft. in height, which as it con- 

 tinues westward expands laterally until 

 at the western end of the research area 

 it is over mi. in width. This hill 

 forms the beginning of the divide 

 between the Mazaruni and the Cuyurii 

 Rivers. In the northwestern part of 

 the research this hill comes close to 

 the shore of the Cuyuni, while to the 

 north and northeast are swamps and 

 moist lowlands. Southward of the hill 

 rolling lowlands predominate and 

 swamps are fewer in number and less 

 in extent. 



Tidal area and shore. The amount 

 of river shore influenced by tide occupies 

 approximately 6000 linear ft., divided as 

 follows : 



feet 



Rocks 300 



Sand beaches 650 



Steep shores with jungle com- 

 ing to the water's edge, tree 

 roots merging with the tidal 



area 1200 



Shallow, mud and sand bot- 

 tomed flats 3850 



The shore is exceedingly diversified 

 as to its physical characteristics, and 

 all conditions of aquatic environments 

 may be found, varying from shores 

 formed of unyielding granite to softest 

 of muddy oozes, and from reeds and 

 mangroves to buttresses of the tallest 

 of jungle trees. 



Water. At Kartabo the Cuyuni River 

 is 2500 ft. in width. The opposite shore 

 of the Mazaruni is over 6350 ft. away 

 from the laboratory. 



The tides on these rivers run from 

 one to 3 mi. an hour while falling, the 

 fall ranging from 6 to 6 ft. At the 

 Station they average about 1\ hours 

 later than they do at the mouth of the 

 Essequibo, 45 mi. away. 



