737 



The astonishing distance at which the little 

 tides of the coast are felt in the bed of the Oroo- 

 noko and of the Amazon*, has been hitherto 

 considered as a certain proof, that these two 

 rivers have only a slope of a few feet during a 

 course of eighty-five and of two hundred leagues. 

 This proof however does not appear irrefragable* 

 if we reflect, that the magnitude of the trans- 

 mitted undulations depends much on local cir- 

 cumstances, on the form, the sinuosity, and the 

 number of the channels of communication, the 

 resistance of the bottom on which the tide flows 

 up, the reflexion of the waters by the opposing 

 banks, and their confinement in a straight. 

 A skilful engineer has recently shown, that, in 

 the bed of the Garonne, the oscillations of the 

 tides go up, as on an inclined plain, far above 

 the level of the waters of the sea at the mouth 

 of the river. At the Oroonoko, the tides of un- 

 equal height of Punta Barima and of Golfe triste 

 are transmitted in unequal intervals of time by 

 the great channel of the Boca de Navios, and by 



* The river of Amazons swells periodically at the strait of 

 PauxiSj 192 leagues from the coast. 



t Mr. Bremontier. At la Reole the tide appears to flow 

 ten toises, at Bourdeaux five toises, above the low water 

 mark near Royan . Yet the tides are the same height at 

 Royan and at Bourdeaux. It were to be wished, that these 

 data could be rectified by a more accurate survey. (Recherches 

 sur le Mouvement des Eeiux, p. 809, § 72 and 83.) 



VOL. V. 3 B 



