735 



fluence of the Carony, sixty leagues from the 

 coast, the water rises one foot three inches. 

 These oscillations of the surface of the river, this 

 suspension of it's course, must not be confounded 

 with a tide that flows up. At the great mouth 

 of the Oroonoko, near Cape Barima, the tide 

 rises to a height of two or three feet ; but farther 



Oroonoko from the mouth of the Rio Mamo (ten leagues above 

 that of the Carony) to Punta Barima, I found 207', while an 

 opening of the compasses of half a degree gave me 186'. We 

 must not hence conclude, that La Condamine and d'Anville 

 are in an error, when, in order to estimate the course of a 

 river, they add in general one quarter or one third. (Jour- 

 nal des Savans, Jan. 1750, p. 183.) This point being of 

 great importance for the construction of maps, I had much 

 satisfaction in being able to verify it recently. The learned 

 commentator on Strabo, Mr. Gosselin, has measured the sinu- 

 osities of the Nile on the great map of the institute of Egypt 

 in forty-seven sheets, with an opening of the compasses of 

 1000 metres, or nearly one third of a nautical league ; and he 

 found the length of the course of the waters from Syene to 

 Damietta 1,180,400 metres, or, at a mean degree, 637' 35" 

 (near 212 nautical leagues of 5562 metres). Geogr. de Strabon, 

 vol. v, p. 308. Now I found 173 leagues, with an opening 

 of the compasses of half a degree, on the fine map of Colonel 

 Leake. The sinuosities of a river, therefore, which is not 

 very winding, were a little more than one quarter. D'Anville 

 adopted this same proportion for the Napo and the Pastaza. 

 In the most tortuous rivers nearly one third must be added, if 

 the length of the course have been measured with an opening 

 of the compasses from 30 / to 1°, that is, suppressing sinuosi- 

 ties less than this space. (La Condamine, Voyagt h I' Amaxvne, 

 p. 67.) 



