1836:] 



variations of the Barometer* 



365 



But, to return to our subject — It appears that the formula exhibits 

 the state of the barometer throughout the year to as great an accuracy 

 as it can be observed, with the exception of the months of October and 

 November : — now these months are particularly distinguished for the 

 dense state of the clouds, and the large quantity of rain (about 26 

 inches) which usually falls, circumstances which, one would suppose, 

 would be more than sufficient to account for four or five hundredths of 

 an inch of the barometer. In addition to the above, I have endeavour- 

 ed to account for the changes of the barometer, by allowing its varia- 

 tions to be expressed by some function of the temperature, of the Sun's 

 declination, and of the altitude ; but nothing like a reconciliation can 

 in any way be produced. On inspecting the Calcutta results it is evi- 

 dent that our formula is altogether insufficient to express the varia- 

 tions there met with ; but it is equally evident that one of a 

 similar nature is necessary ; instituting accordingly the formula 

 h 1 = h + (1 — R) at 7 , and solving the equations of conditions which 

 thence arise, we get 00' = 13.67 inches, which being substituted in the 

 formula, we get 



THE MEAN HEIGHT OF THE BAROMETER AT CALCUTTA, AT 10 A. M. 



From observation. From the formula. Difference. 







Inches. 







30.050 



30.077 



+,027 



February. .. «, 



30.018 



30.018 



,000 





29.928 



29.917 



— ,011 





847 



.848 



+ ,001 





692 



.695 



+ ,003 





591 



.633 



4,042 





562 



.630 



-} ,068 





598 



.686 



4,088 



September . . 



719 



.790 



+ ,071 





29.888 



29.905 



+,017 



November . . 



30.054 



30.013 



—,041 



December.. . 



30.069 



30.074 



-{-,005 



Here the formula agrees well for the first five months of the year; — in 

 June, July, August, and September, (the months in which heavy rains 

 fall — the monsoon in fact) we find, as in the case of the Madras Regis- 

 ter, that the formula gives too large a result. For October (which is a fine 

 month in Calcutta) the formula agrees well — for November I suspect 

 the observations (which it must be recollected are derived from four 

 years observation only) are a little too large, probably ,020; in which 

 case the formula appears to belong, as well to the Calcutta, as to the 

 Madras results. I have already stated that there are no further results 

 to be met with from observations in India, which are suited to this our 



