4 HlSfORT of the SOCIETl*. 



The firft of the obfervations here referred to were made by 

 M. Lamanon, an ingenious naturalifl who accompanied Pey- 

 ROUSE, and who has given an account of them, (fee 4th vo- 

 lume of the Voyage, 8vo edit.), in a letter to M. de Condorcet, 

 dated, St Catherine, 5th November 1785. Dr Balfour's Ob- 

 fervations are in the AJiatic Refearches for 1 744, and a fhort ac- 

 count of them is alio inferted in the 4th volume of the Tratifac- 

 tions, R. S. Edhi. Hifb p. 23. 



M. L a man on's -obfervations were made in confequence of 

 inftrucYions from the Academy of Sciences, directing him to keep 

 an exact account of the heights of the barometer in the vicinity 

 of the equator at different hours of the day, with a view to dis- 

 cover, if poffible, the quantity of the variation of that irritru- 

 ment, due to the action of the fun and moon, that quantity 

 being there probably at its ntatoimum, wldle the variations arifing 

 from other caufes are at their minimum. 



M. Lamanon was provided with one of Nairne's marine ba- 

 rometers, which, he fays, was fo little afFected by the motion of 

 the fhip, that it might be depended on to the T ~ of an inch. 

 In this barometer, he tells us, that from about the nth degree 

 of north latitude, he began to perceive a certain regular motion, 

 fo that the mercury flood higheft about the middle of the day, 

 from which time it defcended till the evening, and rofe again 

 during the night. As they approached the equator, this became 

 more diftinctly perceptible ; and on the 28th of September, the 

 Ihip being then in i° 17' north latitude, a feries of obfervations 

 was begun, and continued for every hour till the lit of October, 

 at 6 A. M. The following abftract mews the refult of the ob- 

 fervations on the 28th and 29th. 



V From 4 to 10 A. M. Barometer rofe 1 /. T °^ 



28th Sept. <From 10 A. M. to 4 P. M. fell 1 -\ 



^From 4 to 10 P. M. rofe o T 9 - 



29th 



