634 



Lieutenant Kenny on the Constants of 



corrections of this monthhave the sign plus (+) ; that the remaining nine months, 

 from February to October inclusive, have (each of them) two moments when 

 the horary corrections vanish. 



Table III. 



Showing the Moments of the Forenoon and Afternoon, when the Horary Corrections vanish. Horary 



Correction = 0. 



The above small Table shows that from February to October inclusive, 

 each month having two moments when the horary correction vanishes, such 

 moments are nearly equally distant from 1 o'clock, p. m., when the errors in 

 excess are greatest ; also, that such moments are near to sunset, and to two 

 hours from sunrise. It is, however, important to know that the time near 

 sunset is more favourable for barometric observations than that of the forenoon. 

 For, in examining the large Table of horary corrections, it appears that the 

 corrections vary more rapidly in the forenoon than in the afternoon, near to 

 the time when the horary corrections disappear. From these facts we learn 

 that in making use of the new formula we require a Table of horary corrections, 

 and that, when no such Table is to be had, we should be careful to make 

 observations near to sunset, or to about two hours after sunrise. 



