r OX THE BAROMETER. 20j 



O-," relating; the above observations to the late Co- 

 lonel Pearce, an indefatigable and rigidly accurate 

 observer, and who had devoted much time and at- 

 tention to Barometrical pursuits, he was surprised that 

 such regular variations of the Mercury should have 

 escaped his observation : but some time after, with 

 great candour acknowledged the certainty of the fact, 

 and framed an hypothesis to account for it; which you 

 will probably be able to obtain on an application to 

 Captain Grace. 



To me the phenomena appear inexplicable to any 

 hypothesis that I can think of. The periods are evi- 

 dently connected with the earth's diurnal motion ; and, 

 if we had not a satellite, might be easily explained by 

 the atmospheria! tides caused by the sun. But when 

 we find that the Barometer is not, in the least observ- 

 able degree, affected by the moon's passage over the 

 meridian, or by the united action of the sun and moon 

 at the syzygies, we have absolute proof that this can- 

 not be the cause; neither can the expansion of the 

 Mercury, being directly opposite to the phenomena, 

 the greatest degree of heat taking place at three o'clock, 

 when the Mercury is lowest. 



„ With respect to the influence of the moon on the 

 atmosphere, I was perfectly satisfied while in Becrboom, 

 that the cold season set in at the syzygies only; and that 



ete was always a considerable increase of cold at every 

 return of them. But at the old powder-works near 

 Calcutta, I observed the greatest degree of cold to 

 happen sometimes at the quadratures. Being, how- 

 ever, at thai time much engaged in other pursuits, I 

 did not attend to the circumstance of the moon's 



absolute 



