682 



The phenomenon of horary variations was 

 observed in 1722, for the first time, and pretty 

 completely ia the tides of day and night, by a 

 Dutch naturalist, whose name has not descend- 

 ed to our times. It is said, in the Literary 

 Journal of tht Hague : " The mercury rises * 

 in that part of Butch Guyana, every day regular- 

 ly from 9 h in the morning to nearly lli h ; after 

 which it descends till towards 2 h or 3 h in the af- 

 ternoon, and then returns to its first height. It 

 has nearly the same variations at the same 

 hours of the night ; the variation is about J of 

 a line or f of a line, at the utmost a whole line. 

 It were to be wished that the philosophers of 

 Europe would male their conjectures on this 

 point." The observations I made seventy-seven 



* See extract of a letter from Surinam, in the series of the 

 year 17*22, p. 234. The observations in that letter prove 

 that the author was occupied in determining the mean height 

 of the barometer at the Hague and at Surinam. After obser- 

 vations of six years, he believes the former to be 336*1 lines, 

 and the latter 336 5 lines (wihout correction of the tempe- 

 rature He also states a ver; remarkable regularity in the 

 hours when the rains begin in Dutch Guyana. <e In the 

 humid season," says he, " the rains at first begin between 

 nine and ten in the morning, anl continue every day till be- 

 tween three and four in the afternoon ; they afterwards begin 

 towards eleven or twelve ; then, towards one or two • and, 

 finally, towards three or four in the afternoon, after which 

 they cease entirely. It very seldom rains in the night ; the 

 air, at break of day, is serene at all seasons." 



