ON THE BAROMETER. 20$ 



that the moon's declination, notwithstanding what you 

 may have heard from other quarters, has any percep- 

 tible effect on the tides. 



I have been the more particular on this subject, as 

 I have heard it made an unanswerable objection to 

 your system, that the first attacks of intermittent fever 

 do happen at the quadratures as well as the syzvgies; 

 and that relapses do likewise happen at the quadra- 

 tures. Now, should you meet with any such cases, 

 the above observations may perhaps tend to reconcile 

 them to vour system, &x. 



John Farquhar. 



Banky Bazar •, 12 th Feb. 1794. 



III. 



Although in this letter Mr. Farquhar de- 

 scribes in the Barometer only three different diurnal 

 periods of rising and falling, I could not help suspect- 

 ing that there must likewise be a fourth^ which had 

 escaped his notice ; and that I should be able to dis- 

 cover a periodical falling also in the state of the 

 mercury, between eleven at night and six in the 

 morning, analogous to that which he had observed 

 between eleven at mid-day and six in the evening. 

 Accordingly, by keeping myself awake, and conti- 

 nuing my observations during the night, I have now 

 the satisfaction to be assured that my anticipation of 

 the revolution I expected to discover, was perfectly 

 just. 



IV. 



With a view of ascertaining the progre:s of th 

 four different revolutions by personal observation, I 



imposed 



