564 Royal Society, 



and the mean of the temperatures of these summers is 64«°'0. The 

 hottest summer was that of 1846, the mean temperature being as high 

 as 65°-0. 



Cold autumns occurred in the years 1814, 16, 20, 29, 36, 37, 38, 

 42, 44, 45, 49 and 50 ; and the mean of the temperatures of these 

 autumns is 47°*8. The coldest autumn was that of 1849, the mean 

 temperature being only 47°'0. 



Hot autumns occurred in the years 1810, 11, 18, 21, 27, 28, 40 

 and 46 ; and the mean of the temperatures of these autumns is 52°*3. 

 The hottest autumn was that of 1818, the mean temperature being 

 as high as 54°*5. 



Cold winters occurred in 1814, 16, 20, 23, 30, 38, 41, 45 and 47 ; 

 and the mean of the temperatures of these winters is iJ4°'4. The 

 coldest winter was that of 1814, the mean temperature being only 

 S2°-7. 



Hot winters occurred in 1822, 24, 28, 34, 35, 46, 48 and 49 ; and 

 the mean of the temperatures of these winters is 41°'5. The hottest 

 winter was that of 1834, the mean temperature being 43°*3. 



" On Depressions of the Wet-bulb Thermometer during the Hot 

 Season at Ahmednuggur, in the Deccan." By Colonel Sykes, F.R.S. 

 &c. 



The author states that he is indebted to Major William Coghlan 

 for the tables of hourly depressions of the wet-bulb thermometer 

 during the months of March and April of the present year, which 

 form the subject of this communication, and which are a necessary 

 supplement to his paper recently published in the Philosophical 

 Transactions. The observations at Ahmednuggur, lat. 19° 05' 

 49" N., long. 74° 48' 10", elevation above the sea 1911 feet, which 

 were undertaken by Dr. Forbes Watson, commenced on the 18ih 

 of March, and were continued to the 14th [of April inclusive. 

 They were made hourly from 6 a.m. to 9 p.m., giving 16 hourly re- 

 cords daily ; but on the 24th and 29th of March, and on the 4th, 

 8th and 10th of April, they were continued throughout the twenty- 

 four hour?. The instruments employed were a dry- and a wet-bulb 

 thermometer, by Adie, perfectly alike and giving precisely the same 

 indications when both were dry, and a self-registering thermometer. 

 They were suspended on a platform attached to a window under the 

 verandah of the house, with a N.W. exposure, and were protected 

 from radiation and reflexion of heat from the ground. As, from 

 some preliminary observations, it appeared that the depression of the 

 wet-bulb varied in every case with the intensity and duration of the 

 draught of air upon it, in each observation a slight current of air 

 was produced by a fan near the mouth of a funnel, the small end of 

 which abutted on the wet-bulb, and the operation was continued 

 until no further depression of the thermometer could thus be pro- 

 duced ; a stronger current of air was then forced on the bulb by 

 means of a large double bellows ; and the result of each operation 

 was recorded. 



To obviate the anomalies which might arise from single observa- 

 tions, and to fix a mean state, for each hour, of the temperature of 



