462 



tude west of the meridian of Paris. What we 

 find in all the zones along the coast occurs in 

 the interior of South-America. Very simple 

 geometric considerations enable us to conceive* 

 that the configuration of the soil, and the im- 

 pulse of the tributary streams, modify the direc- 

 tion of the running waters according to stable 

 and uniform laws. The deltas are the effect of 

 a bifurcation in the plain of a shore; and on 

 observing them carefully, we sometimes find^ 

 near the bifurcation, communications with other 

 rivers, branches of which are in the vicinity. 

 Now, whenever, in the interior of great conti- 

 nents, we find a flat surface like that of a shore, 

 the same phenomena must occur. The causes 

 that produce bifurcations near the mouth of a 

 great river may also give rise to them near it's 

 source, and in the upper part of it's course. 

 Three circumstances contribute toward this 

 principally; the very small undulations of a 

 plain, that contains at once two basins of rivers> 



at 11° 35' from Cayenne ; the real distance is 13° 48'. (See 

 for the bases of these calculations the Rec. d'Observ. Astr., 

 which I published conjointly with Mr. Oltmans, vol. % 

 p. 255 and 261 — 278). These remarks I believe will suf- 

 fice, to lead those who occupy themselves with astronomical 

 geography to perceive, that 1 had some motives for consider- 

 ing the astronomical observations made on the banks of the 

 Upper Oroonoko, the Cassiquiare, and the Rio Negro, as 

 very essential to the improvement of the maps of America. 



