302 



has prevented any readings on either January or February 

 term days, and of a supply of five pints just had up under 

 order of Government, nearly three and a-half pints have 

 evaporated on the journey. So much for an Indian climate, 

 and bottles not hermetically sealed. You will oblige me by 

 acknowledging the receipt of this packet, either through our 

 mutual friend Professor Lloyd, or through the Military Se- 

 cretary at the East India House, Philip Melvill, Esq. ; and 

 if you wish me to alter the system adopted, you have only to 

 say so, and I will endeavour to meet your views. I hope to 

 continue the regular series from this month again without 

 interruption. 



" Believe nie to remain, with kind regards, 

 " My dear Sir, 



" Yours very truly, 



" S. BolLEAU. 



" P. S. — You cau make any use of the accompanying do- 

 cument you may please to do." 



Dr. Apjohnthen observed, that availing himself of the per- 

 mission given him by Captain Boileau, he would make a few 

 remarks upon the hygrometric observations made on the mag- 

 netic term days for 1841. These observations were highly in- 

 teresting to meteorologists, having been made by an officer of 

 great scientific attainments, of extensive experience as an 

 observer, and with the aid of first-rate instruments: but his 

 (Dr. Apjohn's) reason for considering them particularly im- 

 portant was, that they furnished the means of estimating the 

 relative merits of the two hygrometric processes at present 

 in use, viz., that according to which, the dewpoiut is directly 

 got by the aid of Mr. Daniell's instrument, and that which 

 conducts to the same conclusion through the application of 

 the well known formula, 



P-f 



/"=/'_, 01 147 (/-Ox 



30 



* In this expression f is the force of vapour at dew-point, f the force of 



