146 Royal Society, 



3. " An Account of Meteorological Observations in four Balloon 

 Ascents made under the direction of the Kew Observatory Com- 

 mittee of the British Association." By John Welsh, Esq. Com- 

 municated by Colonel Sabine, R.A., Treas., V.P.R.S., President of 

 the British Association, on the part of the Council of the Asso- 

 ciation. 



The object contemplated by the Kew Committee in the balloon 

 ascents, of which an account is given in this communication, was 

 chiefly the investigation of the variations of temperature and humidity 

 due to elevation above the earth's surface. Specimens of the air at 

 different heights were also obtained for analysis. 



The instruments employed were the barometer, dry- and wet-bulb 

 hygrometer, and Regnault's condensing hygrometer. 



The barometer was a siphon, on Gay-Lussac's construction, with- 

 out verniers ; the upper branch of the siphon being alone observed, 

 corrections having been previously determined for inequality of the 

 tube at different heights of the mercury. 



Two pairs of dry and wet thermometers were used, one pair having 

 their bulbs protected from radiation by double conical shades open at 

 top and bottom for the circulation of the air, the surfaces being of 

 polished silver. The second pair were so arranged, that by means 

 of an " aspirator," a current of air was made to pass over the bulbs 

 more rapid than they would be exposed to by the mere vertical 

 motion of the balloon. The object of this arrangement was to 

 enable the thermometers to assume with more rapidity the tem- 

 perature of the surrounding air, and also to diminish the effect of 

 radiation, in case the shades should not be a sufficient protection, 

 especially when the balloon was stationary or rising very slowly. 

 The thermometers used were very delicate, the bulbs being cylinders 

 about half an inch long and not more than jgth of an inch diameter. 

 It was found on trial that when the bulbs were heated 20° above the 

 temperature of the air in a room, they resumed their original reading 

 in 40 or 45 seconds, when moved through the air at the rate of 5 or 

 6 feet in a second. It is thus probable that any error arising from 

 want of sensibility in the thermometers will be small, and in all like- 

 lihood not more than may be expected from other accidental causes. 



The observations were taken at short intervals during the ascent, 

 it having been seldo'm practicable to obtain a regular series in the 

 descent. The intervals were generally one minute, but frequently 

 only 30 seconds, so that an observation was for the most part 

 recorded every 200 or 300 feet. All the observations are given in 

 detail in the tables accompanying the paper. They are also given 

 in the graphical form in the curves. 



The ascents took place on August 17, August 26, October 21, 

 and November 10, 1852, from the Vauxhall Gardens, with Mr. 

 C. Green's large balloon. 



The principal results of the observations may be briefly stated as 

 follows : — 



Each of the four series of observations shows, that the progress 

 of the temperature is not regular at all heights, but that at a certain 

 height (varying on different days) the regular diminution becomes 



