372 REPORT — 1866. 



nearly twenty minutes, the temperature was 35°, or about 6° warmer than 

 ■when at the same elevation something more than one hour before. On turn- 

 ing to descend, the temperature changed very little, it being 35° to 36° for a 

 thousand feet downwards. It increased to 37° at 4500, to 47° at 1500, and 

 to 54° at 900 feet ; but here the increase was checked, and at 600 feet the 

 temperature was 52|° ; on ascending a little again the temperatiu'e increased, 

 and decreased on descending, and was 50^° on the ground at a spot 300 feet 

 above the sea, at half-past eight o'clock. At Greenwich at this time the 

 temperature of the air was 52°. 



At the time of leaving the earth at 6'' 14™ the air at Greenwich had but three 

 grains of moisture in a cubic foot. At AVindsor, near the Thames, there were 

 4| grains ; the air was damp : on ascending the air at first became drier ; 

 but at the height of one mile was saturated, and was very nearly saturated at 

 the same height after sunset. 



Thus this double ascent enables us to compare the temperatures of the same 

 elevations, just before and just after sunset on the same daj", and to estimate 

 the amount of heat radiated from the earth at about the time of sunset. 



At heights exceechng 2000 feet the direction of the wind was N. by "W. ; 

 at the height of one mile the au- was nearly calm ; and at heights less than 

 2000 feet it was N. by E., and these cm-rents were met with always at those 

 elevations. 



At all times during the ascent, whenever the sun shone upon a transparent 

 bulb, or a dull blackened bulb thermometer, the reading was a very little 

 in excess of the reading of a shaded bulb, and was frequently the same even 

 when the sun's heat felt sensibly warm to ourselves. 



The path of the balloon from Windsor was over Windsor Great Park ; 

 nearly over AVoking at 7'' 43™ ; a little west of Guildford, approaching the 

 coast, at half-past nine, we calculated that the sea must be near, and we 

 descended at a place five mUes south of Pulborough. 



My attention was almost wholly occupied with the observations, Mr. "West- 

 car's was chiefly with the management of the balloon, frequently, however, 

 reading the several instruments, particularly those whose bulbs were exposed 

 to the sun's rays. 



The safety lamp was burning all the time, thus enabling the instruments to 

 be read after dark. 



I till recently believed that this was the first ascent for scientific purposes 

 since that of Biot and Gay-Lussac in 1804, in which the management of the 

 balloon was undertaken by the experimentalists themselves. But I find I am 

 in error in this respect. My friend L'Abbe iloigno tells me jthat Messrs. Bixio 

 and Barrel, in the year 1850, took the entire management of the balloon in 

 their own hands. 



On descending one hour and a half nearly after sunset, there was no one 

 near to assist us to empty the balloon and to pack it. This we had to do 

 ourselves, and were preparing to pass the night in the car of the baUoon, 

 when towards midnight a shepherd came to attend sheep, and we passed the 

 night in his cottage at the distance of half a mile, leaving the balloon, &c. in 

 the fields till the morning. 



This is the last ascent of which I have to speak. I regret that I have not 

 been able to report upon others, but it is all I have possibly been able to make 

 in the year. 



From aU the experiments made it would seem that the decrease of tempe- 

 rature with increase of elevation is variable throughout the day, and variable 



