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riments at each place, will give the precife length of a pendulum flriking feconds on 

 the equinox at the level of the fea, that length the moll proper, by common confent, 

 to be received as a univerfal meafure. How defirable, indeed, were fuch a meafure, 

 at leall for mathematicians ! ^ The diverfity of tongues, an inconvenience which yet 

 muft endure for many centuries, does it not prefent fufficient obftacles to the progrefs 

 of the fciences and the arts, by prefenting, in a degree, the requifite communication 

 between different people ; but it muft be ftill increafed, as one may fay, purpofely, by 

 an affedation of ufmg, in each country, and at each fpot, meafures and weights which 

 conftantly vary one from the other, while nature, in the pendulum ftriking feconds 

 under the equator, prefents an invariable teft, fo well adapted to the eftabliihment of a 

 common meafure and a common weight in every country j one, too, which calls upon 

 every lover of learning for its adoption ? 



The objed of my firft folicitude on reaching Cayenne was, to diftribute to various 

 perfons feeds of Quinquina, or the Bark-tree, then only eight months old ; by means 

 of thefe, I trufted to repair the lofs might be experienced by the failure of the young 

 plants of that tree, the laft of which, preferved by me from the heat of the climate and 

 the cafualties incident on fo long a voyage, had been carried away by a wave which, 

 off Cape D' Orange, threatened our canoe with deftrudion. The feeds at Cayenne did 

 not profper ; indeed, reflecting on their delicacy, and their inevitable expofure to a 

 high temperature, their profperity was more than could reafonably be expeded. I have 

 not, moreover, received any information refpeding the refult of thofe I committed to 

 the management of the Jefuit miffionaries on the Upper Oyapoc, the mountainous ter- 

 ritory and more temperate climate of whofe eftabliihment affimilated, far more than 

 Cayenne, with that of Loxa, whence the feeeds were brought. 



At Cayenne I obferved the latitude to be, as determined by M. Richer, 5° 56' N. ; 

 but was at firft furprifed to find, by four obfervations of the firft fatellite of Jupiter, 

 each of them agreeing with the others, that the difference between the meridians at 

 Paris and Cayenne is nearly one degree lefs than is ftated in the Connuiffance des Temps ; 

 but I have fince learnt, that M. Richer made no obfervation of the fatellites of Jupiter 

 at Cayenne, and that the longitude of this place was deduced from other obfervations 

 made by him, in a manner very imperfed and much fubjeft to error. A more enlarged 

 detail on this fubjed, as well as of my remarks on the tides, and the variation and 

 dipping of the needle, made at the fame place, will more appropriately occur at our 

 private meetings. 



Noticing that at Cayenne, the mountains of Courou, eftimated ten leagues diftant, 

 were very diftindly vifible, I conceived, that a fpot, whence the flalh and report of a 

 cannon fired at the fort of Cayenne could be perceived, would be well adapted to the 

 menfuration of the celerity of found in a climate fo different from that of Quito, where 

 we had made a variety of experiments. M. d*Orvilliers, commandant of the fort, not 

 only complied with my requeft of iffuing the requifite orders, but gladly undertook 

 to Ihare the toil with me on the occafion ; M. Frefneau, of the engineer corps, under- 

 took, on his part, the hoifting of fignals, and afcertaining the celerity of the wind, 

 with feveral other incidental matters. From five experiments made on two different 

 days, four of which agreed within lefs than half a fecond in one hundred and ten, and 

 from the diftance, which was concluded to be twenty thoufand two hundred and thirty 

 toifes by trigonometrical calculations, in which a bafe twice meafured on a level beach 

 of one thouland nine hundred toifes was employed, we determined, as the mean refult 

 of the celerity of found, deduding for that of the wind, that it flew at ihe rate of one 

 hundred and eighty-three and a half toifes in a fecond in this part, whereas its progrefs 



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