96 



autumns is 4<7°*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 34°*4. The 

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

 32°-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. 



12. "On Depressions of the Wet-bulb Thermometer during the 

 Hot Season at Ahmednuggur, in the Deccan." Bv Colonel Sykes, 

 F.R.S. &c. Received June 17, 1851. 



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 18rh 

 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 hours. 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 

 the air, the temperature of evaporation, and the mean depression of 

 the wet- bulb, the means of these elements have been taken and are 

 presented in a table. In this table are also given the dew-points as 

 determined by means of Mr. Glaisher's factors and by Dr. Apjohn's 



