THE RIVER DORDOGNE, JSf^ 



each other clofely, and which occupy the whole breadth of 



the channel. Thefe waves advance with a prodigious rapidity, >\hich ruft 



break and overturn every thing which oppofes them. I have ^"''"'af'l ^uh 

 /• • /■ I 1 <• 1 , • . B"^^^^ rapidity, 



leen m lome places a. large exjent or Jandcarrted away, great and overtura 



trees torn up by the roots, and ravages of all kinds committed; everything 



every where that they pafs the banks are fwept clean ; the them, carry 



canoes, the pirogues, and even the barks can only efcape their a^^ay large por- 



fury, by anchoring in deep water. After having examined j^" j^ °^^^ ^^^^ 



this phenomenon with attention in different places, I have aU up trees by the 



ways remarked that it only takes place, when the rifing flood ]|°°q^*i ^ 



is engaged in a narrow channel, or meets in its way with a in narrow chan- 



bank of fand, or a (hallow place, which occafious an obftacle "^'V °^^^ !f "*^ 

 1 • . /• • . 1 . - • , banks, or /hal- 



to it ; that it was in thole places alone that this impetuous and low places. 



irregular movement of the waters commenced, and that it 



"ceafed a little beyond the bank, when the channel became 



deeper, or grew confiderably wider. It is faid that fomelhing it ceafed where 



fimilar to this happens at the ifles of the Orcades, at the north ^^^ channel 



of Scotland, and at the entrance of the Garonne, (it fiiould be or wider* 



the Dordogne), in the vicinity of Bourdeaux, where the ef- 



fe<5ls of thefe tides, is called a Mafcard." 



It appears from what has been cited from M. Condamine, 

 that the effefts of the^Pororoca are almoft the fame as thofe of 

 the Mafcaret. Neverthelefs there is a marked difference be- Difference be- 

 tween them in this refpefi, that on the Dordogne, two l^hids ^^"^"^^^^^'^^ 

 of floods take place, one which extends over the whole river, Pororoca. 

 and is fimilar to that which M. Condamine has obferved, 

 and the other which ranges along the (liore, rolling more over 

 the depofits which the waters have left, than in the water itfelf. 

 He fays pofitively in page 19 i, that " at one or two leagues 

 a frightful noife is heard, which announces the Pororoca ; ^s 

 it approaches the noife encreafes ; and fooa an accumulation 

 of water appears from 12 to 15 feet high, and then another 

 that follows, which occupies the whole breadth of the chan- 

 nel". On the Dordogne the Mafcaret rifes with great noife, further partlca- 

 fometimes along the coaft in an elongated accumulation, and l^rs of she Maf- 

 fometimes in the form of frightful waves, which extend over 

 tlte whole river; when it follows the (hore it only appears in 

 the re-entring angles, and on the fand banks, as is defcribed 

 in the (ketch of the plan of the river, which aGCompanies this 

 account, and which lakes in. the whole extent where the ef- 

 fefls of the Mafcaret are perceive J,. The parts covered with Defcrlptlou of 



^n,^I]thetketchof 

 the courfeorthe 



