336 
LIEUT.-COLONEL SYKES’S DISCUSSION OF METEOROLOGICAL 
meter, and the greatest daily and monthly range, occur in the same month at Doda- 
betta, namely, January 1848. The lowest temperature in the year was 38°'5, the 
highest 67°, and the annual range 28°’5. The greatest monthly range was 24°'3. 
Aqueous V apour. 
Preliminary to the discussion of the question of aqueous vapour, a few words are 
necessary on the caution requisite in generalizing on a limited number of facts, or 
on observations not extending over lengthened periods of time. The hourly observa- 
tions of the wet bulb at Madras and Bombay, for 1843 and 1844, are apparently 
trustworthy and satisfactory, supposing the wet bulb theorem to be correct. Those 
at Calcutta were taken only twice daily, at O’* 40™ a.m. and 4 p.m., and how far obser- 
vations, taken twice only during the daytime, can be relied upon for the expression 
of normal conditions, will best be shown by the following comparison of observations 
of the wet bulb at Dodabetta at 8640 feet above the sea-level. The regular meteoro- 
logical observations were recorded twice a day only, at 9^‘ 40™ a.m. and 3'' 40™ p.m., 
but on one day in each month independent observations were taken for twenty-four 
consecutive hours. In a table I have compared the means of the 9^ 40™ a.m. and 
3 I 1 4 om P.M. observations with the means of the twenty-four consecutive hours for the 
same day. The discrepancies are considerable, and too numerous to admit of the 
supposition of their resulting from accident or carelessness. On the 21 st and 22 nd of 
January the hourly observations give a depression of the wet bulb of 9°‘2. The twice 
a day observations give a depression of 9°'4 ; on the 21 st and 22 nd of March a de- 
pression respectively of 5°‘7 and 7°’7 ; on the 21st and 22 nd of April of 5°‘2 and 4°'2; 
on the 21 st and 22 nd of May of 1°’8 and 1°'33 ; and on the 21 st and 22 nd of November 
of 7°‘8 and 6 °T. A bare inspection of the several hygrometric records for Dodabetta 
wdll show the anomalous results in working out the dew-points, elastic force of vapour, 
and per-centage of vapour or fraction of saturation in the atmosphere by the tables 
founded on Dr. Apjohn’s formula. The hourly observations also demonstrate, that on 
the same day, in a transient fog without rain, there shall not be any depression what- 
ever of the wet bulb ; while in the course of the twenty-four hours there may be a 
great depression. For instance, at noon, on the 21 st of December 1847, there was not 
any depression, but at 9 the next morning there was a depression of 3°-2, the mean 
being 1 °' 6 , while the mean of the twenty-four hours was 0°'7. At the former hour 
there was a fog, at the latter, partly a blue sky. Again, at 5 p.m., on the 21 st of No- 
vember, the depression was 1°'5, but at 8 p.m. the depression was 10°'9, the mean 
being 6 °‘ 2 , the mean of the twenty- four hours 7 °‘ 8 ; in both cases there was nearly a 
blue sky. At noon, on the 21 st of July, there was not any depression in a fog; at 
5 A.M. of the 22nd a depression of 2°'0, and yet it was raining. On the 21st of April, 
at 8 P.M., the depression was nil, an hour after it was 5°’5 ; at both hours with nearly 
a blue sky, while at 7 a.m. of the 22nd the depression was 9°'5, with a cloudy sky. 
Supposing these to have been the only observations available for the respective days, 
