Proceedings of the British Association, 223 



differently affected by heat (as those of sea and land), and possessing 

 different retaining and radiating properties. Within the tropics, the 

 well-known regular recurrence of land and sea breezes for many 

 months made it obvious, that a double progression in the diurnal 

 variations of the force of the wind must exist, — and rendered it pro- 

 bable that a double progression of the gaseous pressure would also 

 be found. It was, therefore, with pleasure that he received from 

 Dr. Buist a copy of the monthly abstracts of the two-hourly me- 

 teorological observations made at the observatory at Bombay, accom- 

 panied by a copy of his Meteorological Report for that year, giving 

 a full account of the periodical variations of the wind ; and in the 

 explanations thereby afforded of the diurnal variations of the 

 gaseous pressure at Bombay — which, although at first sight more 

 complex than at the stations of Toronto, Prague or Greenwich, 

 Colonel Sabine conceives to be equally traceable to variations of the 

 temperature. The Observatory at Bombay is situated in the Island 

 of Colabah, in north latitude 18° 54', and east longitude 72° 50', at an 

 elevation of 35 feet above the level of the sea. Col. Sabine then 

 described the tables as received, and the reductions to which he sub- 

 jected them. The sun at Bombay is vertical twice in the year, viz. 

 in the middle of May and towards the end of July. The rainy sea- 

 son sets in about the commencement of June (in 1843 on the 2nd of 

 June,) and terminates in August ; but with heavy showers, of no 

 long duratipn, continuing into September. During the rainy season, 

 and in the month of May, which commonly precedes it, the sky is 

 mostly covered with clouds, by which the heating of the earth by 

 day and its cooling at night by radiation are impeded, and the range 

 of the diurnal variation of the temperature lessened ; and the 

 strength of the land and sea breezes in those months is also com- 

 paratively feeble, — sometimes almost without alternation. For these 

 reasons he has, besides the tables, collected into one view the means 

 of the months of May, June, July and August, or the cloudy months, 

 in order to contrast them with the months of November, December, 

 January and February, when the sky is for the most part clear. 

 These reductions being made, the diurnal variation of temperature is 

 found to have a single progression, being a minimum at 18 hours 

 (6 o'clock, a.m.,) and a maximum at 2 hours ; the average difference 



2 G 



