1832.] in the vicinity of Dehli. 507 



The observations in table II, were made at various places within the 

 limits already mentioned. The mean temperature of each month has 

 been deduced generally, from the observations at sunrise and 2£ p. m. ; 

 but occasionally (when others were wanting) from the observation at 

 sunset only ; in the latter case 3° have been deducted from the tem- 

 perature at that time ; as I find from the mean of a long series of 

 observations, that the temperature at sunset is 3° above the mean of 

 maximum and minimum. For the temperature of the night I have 

 taken the mean of sunset and sunrise. 



In Table III, for the dew points (headed S in the table) I have used 



D • • 9S3 B \ 

 the formula (/== F' — 6056 — = — — - Jgiven in the Gleanings for 



Li 30 ' 



July 1829, page 192, altering the constant 6.056 to 5.84, for, when I 

 received this number of the Gleanings, having by me Daniell's Meteo- 

 rological Essays, and finding that the table of the force of vapour 

 there given, page 596, differed from the one used by the author of the 

 valuable paper above referred to, I had the curiosity to calculate the 



value of " (see the paper same page) and found it = 5.84 ; the dif- 

 ference is not perhaps very material, but as I have always used the 

 table of the force of vapour given in Daniell's Essay above quoted, I 

 thought it more consistent to use the constant modified accordingly. 

 The two last columns of table III, (mean dew point and mean compa- 

 rative tension) have been thus formed : the mean dew point is the 

 mean of all the observations (or rather of all the results derived from 

 the wet thermometer depressions) for several months : the force of 

 vapour answering to the mean dew point, divided by that answering 

 to the mean temperature of the month, gives the mean comparative 

 tension. I have adopted this mode, not only from my having by neces- 

 sity or choice so often altered my hours of observing, but from the 

 consideration that as the dew point generally varies but little during 

 the day, it appeared to me that it would be more accurate to deduce 

 the mean comparative tensions from even one observation of the dew 

 point and the mean temperature, than by taking it as the mean of 

 results calculated for any two or more hours, not excepting even sun- 

 rise and 2£ p. m. How far I may be right in this, I leave to more 

 competent judges to decide. 



Table IV, is nothing more than an abstract of table III, the force of 

 vapour at the dew point being substituted for the dew point itself. It 

 appears, that May is the driest and August the dampest month, consi- 

 dering the comparative tensions as the fairest scale of the humidity of 



