BRITISH GUIANA AND BRAZIL SMITH 339 



fitted to one another, and finally to the adjusted boundary. The 

 results were very encouraging. The finished boundary cut was used 

 as a line of communication for the carriers. As this increased in 

 length, another creek farther to the east would be explored and 

 opened up from its lower end, and a depot of rations placed as near 

 the boundary as possible. When this was found by the locaters, 

 the old line of communication was broken and the new one used. 



The astronomical stations offered a welcome rest from energetic 

 traversing. Moreover the big clearing necessary for a glimpse of 

 the sky permitted kit, bedding, instruments, and books to be dried 

 in the sun. Observations were made by a 314-inch Tavistock theodo- 

 lite for exmeridian longitudes and circummeridian latitudes. The 

 criterion was a probable error of about 0.^02 of time and O.^'S of 

 arc respectively from means of 18 to 24 pairs of stars. Observations 

 for azimuth were also taken. 



Over 85 miles of boundary were surveyed and marked eastward 

 from the source of the Oronoque during the season 1936-37. In the 

 meantime the Brazilians progressed westward from Aramatau source. 

 At the beginning of the following season the cuts were joined and 

 the British struck westward from Oronoque source toward the head- 

 waters of the Essequibo. Next season ought to see the field work 

 completed, and the surrender of this fascinating but rather trying 

 part of the world once more to nature. 



The temperature on the forest floor has surprisingly small diurnal 

 or annual variations. Midday temperatures are 88° to 90° F., mid- 

 night 82° to 84° F., with a 2° variation between midsummer and 

 midwinter values. The humidity is very high, occasionally reaching 

 saturation point, when small gray clouds of vapor form and drift 

 between the trunks. This high humidity is one of the most un- 

 pleasant factors of bush life. To perspire gives no relief; clothes, 

 bedding, and food are perpetually damp, and books fall to pieces 

 after a few months. Unprotected metal corrodes overnight, and 

 leather and glass grow whiskers of mold at an alarming rate. 



Photography is beset with difficulties, and disappointments must 

 be expected. Tlie shutter mechanism and diaphragm of a camera 

 corrode rapidly in the damp atmosphere, and finally cease to function. 

 All glass is attacked by a black fungus which spreads and engraves 

 its surface in blotches and spidery lines. On fine days intense sun- 

 light filtering through the forest roof produces a brilliant dapple 

 of dazzling contrast to the gloom of the forest floor. For this reason 

 the best results are obtained by long exposures in slightly overcast 

 weather. These are made possible by the absence of breeze on the 

 forest floor. 



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