ON THREE BALLOON ASCENTS IN 1864 AND 1865. 147 



say that I succeeded in three only. The first of these "was on December 1st, 

 the second on December 30th, 1864, and the third on February 27th of the 

 present year. These three ascents were made from Woolwich Arsenal. 



Although I have so few ascents to speak of, it must be borne in mind that 

 winter is the most difficult season of the year to pursue balloon experiments ; 

 yet as mountains are not climbed at this time of the year, and so few 

 experiments have hitherto been made by means of the balloon, we are in 

 almost entire ignorance of everything connected with the higher regions of 

 the atmosphere during this cold portion of our year, in respect to the pro- 

 gressive diminution of temperature with elevation, the diffusion of vapour 

 in the atmosphere, the density of clouds, their extent, and the currents in the 

 atmosphere. 



It is therefore the most important season for experiments ; and these will 

 be exceeded in value only by night experiments. 



Ascent from Woolwich Arsenal, December 1, 1864. — The balloon left the 

 earth at 2 h 37 m p.m., the temperature of the air at the time being 48° ; and 

 this value remained almost unchanged till the height of 600 feet was passed 

 (increasing slightly in fact at first), and then very gradually declined to 31 1° 

 at about one mile in height. 



Ascent from Woolwich Arsenal, December 30, 1864. — The balloon left at 

 2 h 13 m p.m., with a temperature at the time of 42^° ; it declined 2° in the 

 first 500 feet ; at 1000 feet high it was 37°, or showing a decrease of 5|° ; 

 at 2000 feet it was 33|°, showing a further decline of 3|° in this 1000 feet. 

 At 2500 feet high we met with cloud ; the temperature was 31°. At 3300 

 feet, just at the upper surface of the cloud, the temperature was 27° ; on 

 getting above the c^ud the temperature rose, and when 400 feet above it had 

 increased to 31 1°. 



Ascent from Woolwich Arsenal, on February 27, 1865. — We left the earth 

 at l h 58 m p.m. ; the temperature of the air was 52°, declined gradually to 35°, 

 when cloud was reached, which proved to be 1000 feet in thickness ; during 

 the passage through it there was no change of temperature, but on passing 

 above it the temperature increased with the elevation. 



By comparing these results with those taken in the period of summer they 

 differ very greatly, and plainly show that the laws of temperature holding 

 good at one season are different from those at other seasons of the year. 



The balloon's courses in these three ascents were very nearly the same 

 after attaining a certain elevation. On the 1st of December, on reaching 

 1100 feet, the current of air changed from W. to S.W. ; at 2000 feet a 

 W.N.W. current was entered ; at 5000 feet the air was moving W.N.W., 

 and we approached the sea, compelling us to descend near Rochester at 

 4 U 25 m p.m. 



In the second ascent the wind was nearly south on the earth when the in- 

 flation began ; it changed to W. nearly, and pilot balloons at a moderate ele- 

 vation moved N,W. On leaving, the balloon first moved E.N.E. ; when 500 

 feet high we entered a W. current, and, as before, moved towards the sea. It 

 was at first intended to descend near the river Thames ; but on coming within 

 300 feet of the earth the wind changed and we went somewhat inland, and 

 descended, at 3 h 20 m , near to Stamford Le Hope. 



During the month of January, and the greater part of February, as far as 

 could be determined from daily observation from the Royal Observatory, 

 Greenwich, the general prevalence of the wind in the higher regions of the 

 ah- was W. and S.W. On February 27th the direction of the wind on the earth 



