THE RIVER DORDOCNE. J^-^ 



the Gironde. The two rivers then defcend together from 



Bee d'Ainbcs to the fea in a diredlion from the eaft to the 



north-weft. All the waters which arrive from the arm of the 



Tea or from the river, advance in a ftraight line with abundance 



into the mouth of the Dordogne, inftead of mounting up the 



Garonne, which runs almoft north and (outh as far up as Bour- 



deaux. The greateft part of the waters which are advancing 



to the Garonne, ought then, when the current has taken its fuppofed to be 



courfe^ to run up the Dordogne at the beginning of the flood, ""J^!^ ^^^ '^^^ 



fince its velocity does not allo'v them time to turn up the Ga- way to the 



ronne : and thus the water which ought to eo to the Garonne, Garonne, taking 



• ,- ..11 . • /f rf ^^ ftraighter 



runnnigup the Dordogne, form by their abundance, this eitect courfc up the 



which Condamine recites : He fays that «' the tides, which Dordogne. 

 ufually take fix hours to rife, arrive at their full height in one 

 or two minutes". But on the Dordogne, the tides never come 

 to their higheft level in near fo ftiort a time, even when the 

 waters are loweft ; but in one or two minutes they encreafe 

 confiderably ; which encreafe is probably caufed by the waves^ 

 which arrive almofl inftantly ; and the flood raiting their maffes 

 of water above their natural level, leaves them there to aug- 

 ment the water in the bed of the river in proportion to tlieir 

 bulk. I After the Mafcaret has pafled, the waters of both rivers 

 encreafe in the fame gradual manner as thofe Qf aU other 

 rivers. 

 M. Sorbie Hkewife thinks, after all, that the tideof the Gironde It may a!fo kc 



may be the caufe of the Mafcaret on the Dordogne, for it pours '^.^"^^t ^y ^jj* 

 • • ■ , r , ^ , ■ • , o ■ . ''<ie of the Gi- 



lts waters into the mouth of the Dordogne in almoft a right ronde rufhing ia 



line; this arm of the fea being at lead fix times larger and * '^'g^c line int* 



deeper than the Dordogne, ought at the flood to carry up fuch the Dordogne, 



an abundance of water, as could not enter into the bed of this »"<! '>y the 



river without occafioning the accumulation of waters defcribed. t^L river * ° 



The phyfical caufe then of the Mafcaret is the confiderable 



mafs of water which arrives from (he Gironde into the mouth 



of the Dordogne, and the fmall depth of this river ; fince it 



is known that in rainy feafons, and when the river is a little 



encreafed in fize, this circumftance never takes place; 



M. Sorbie remarks in conclufion that the fia^ls related (hew remarks on the 



evidently that the flowing and ebbing of the tides of rivers J*^" ''//'""J* 



■' o " fuppofed to be 



are diiferent from thofe of the fea; that the ebbing and flowing caufed by the 



of rivers, are only fecondary eflFeas of the iidei of the fea ; "'^^ °f ^^^ ^^* 

 . . . ^ , ■' - ■•'.., e IV forming a daA 



that IS to lay, that the waters ot the lea only form a dam to acrois theif 



Vol. XIII.— FEaRCA&Y. iSOfl. N thofe courfc 



