35^ ^« '^^ Itifluenee of the Sun 



at its maxmum far the week preceding and following, about 

 the time of either quarter; and to be either falling or at its 

 minimum for the two weeks, about ihe new and full. It is 

 rei-narkable, that the point of greateft depreflion during the 

 year, viz. to 28,67, is found about twelve hours after the 

 new moon on the 8th of the eleventh month ; and that of 

 its greateft and extraordinary elevation to 30,89 an the 7th 

 of the fecond month at the time of the laft quarter. More- 

 over, this coincidence appeared to obtain the moft regularly 

 in fair and moderate weather ; and, in general, when the 

 barometer fell during the interval between the new or full 

 n>oon and the quarters, an evident perturbation in the atmo- 

 fphere accompanied ; of which may be inftanced 11. 15 to 

 23, when the barometer, after an uncommon rife, continued 

 to fitll rapidly after the new moon, with fevere cold, which 

 ended fuddenly in ftormy and wet weather ; again, VI. 14 

 to 20, when two weeks of fair weather ended in a thunder- 

 florm. In the greater part of XII. the ufual coincidence 

 difappears, and the converfe takes place, the barometer 

 being low at the quarter and high at the full, amidft cori- 

 tinued alternations of rain, froft, and fnow ; and, for part 

 of the time, high winds. The remarkable depreffion be- 

 tween the 24th and 2Sth was attended with intenfe cold, 

 the thermometer being noted on four fucceflive days at 15°. 

 i4°. (f. 13°. refpeftively. On the two days preceding the 

 laft quarter, the barometer rofe rapidly, and rain followed ! 



In the feventh month, which was wet and windy through- 

 out nearly, there is the leaft of this coincidence to be feen. 

 Inftances may be obferved in which the tendency to rife or 

 fall at the times pointed out, after being interrupted by an oc- 

 cafional caufe, is refumcd. On the whole I thought there 

 appeared fufficient ground, on the evidence of the year 1798, 

 to fuppofc that the gravity of our atmofphere, as indi- 

 cated by the barometer, mav be fubjeft to certain periodical 

 changes, effefted by a caufe more fteady and regular thaa 

 either change of temperature, currents, or folulion and pre- 

 cipitation of water, to which I believe the vchole variation 

 has been heretofore attri!)uted. To difcover thefe periodical 

 changes^ if polfible, and to afcertain their amount, inde- 

 pendently 



