IN SOUTH AMERIOA. 2$^ 



de la Mef, a book tranflated from all languages, and which, in this part, feems rather 

 calculated to miflead than afford any light to navigators. At length, at the approach of 

 the full moon, the commencement of the fame bore fo much dreaded fet us afloat, but 

 not without much danger, as it drove the canoe before it. and Caufed it to pitch and 

 labour more in the mud, and with even greater velocity, than I experienced while in 

 the currents of the Pongo in the upper part of the river I had lately navigated, of 

 which, at length, I faw the mouth. Here my chart of the Amazons river finifhed ; I 

 continued, however, to take a plan of the coaft, and to make my obfervations of the 

 latitudes, as far as Cayenne. 



At a diftance of fome leagues weft of the bank and under the fame parallel, 

 I found a fecond mouth of the Arauari, now barred by the fands. This mouth, 

 and the deep and broad channel leading to it from the north, with the iflands 

 in advance of the cape northward, are the river and bay of Vincent Pin9on. The Por- 

 tuguefe have their reafons for confounding it with the river Oyapoc, the mouth of 

 which, by Cape D* Orange, lies in latitude 4° 15' N. ; yet, notwithftanding the article 

 of the treaty of Utrecht confounds the Oyapoc with the river of Pin9on, regarding 

 them as one, they are neverthelefs fundered by a fpace of more than fifty leagues. This 

 is a fad that will not be difputed by any who have confulted the old charts of this 

 * country, and have read the original authors who wrote on America before the eftablifli- 

 ment of the Portuguefe in Brazil. I found, by obfervations made on the 23d and 

 24th of February, that the French fort of Oyapoc ftands in latitude 3° 55' N. : its 

 fite is on the north bank of the river, fix leagues up from its mouth. 



At length, after a voyage of two months by land, I may fay, as well as by fea, (for 

 the coaft is fo flat between Cape North and the ifland of Cayenne, that the rudder 

 conftantly grounded, or rather, never ceafed furrowing the mud, as half a league from 

 fhore there was at times no more than a foot of water,) I arrived at Cayenne on the 

 36th February 1744. 



It is well known, that it was in this ifland M. Richer of this academy, in 1672, made 

 difcovery of the inequality of weights under diflferent parallels, and that his experiments 

 were the bafe'of the theories of Mr. Huygens and Sir Ifaac Newton refpedting the 

 figure of the earth ; now, one of the motives which induced me to go to Cayenne, 

 was a profped of the utility that would refult from a repetition of his experiments, as 

 we are in the prefent day greatly accuftomed to them, and enabled to exercife far more 

 precifion than formerly. I bring with me a fteel rule, which, according tg my obfer- 

 vations, is precifely of the fame length with the fimple pendulum at Cayenne ; but I 

 look for ftill greater eyaditude, from a comparifon of the number of the ofcillations of 

 my fixed pendulum at Cayenne with the vibrations at Paris of the fame pendulum in 

 equal fpace of time, when I fliali be enabled to make the experiment. This compari- 

 fon will fliew the pbfitive excefs of the number of the vibrations of the pendulum at Cay- 

 enne over thofe of the pendulum vibrating feconds at Paris, the length of which is 

 determined by M. Mairan ; and as more precifion was obferved by him in the afcertain- 

 ment of the length of this pendulum than any by whorn he had been preceded, it is fair to 

 prefume it is corred. As an eftabliftied term may alfo be regarded the length of the 

 pendulum afcertained at Quito, in various manners, and with different inftruments, by 

 M. Codin, M. Bouguer, and myfelf, in which length we feverally agree to within lefs 

 than the hundredth part of a line. But, from whichever point we proceed, the dif- 

 ference between the number of ofcillations in the fpace of twenty-four hours of the 

 fame pendulum at Quito, at Para, and at Paris *, determined by a long feries of expe- 



* It is queftionable, whether, in lieu of « Paris," (hOuld not be re'ad « Cayenne." Tr. ^ 



riments 



