Scientific Intelligence — Meteorology. 365 



METEOROLOGY. 



10. An Account of Meteorological Observations in four Balloon 

 Ascents made under the direction of the Kew Observatory Committee 

 of the British Association ; by John Welsh, Esq. Communi- 

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

 British Association, on part of the Council of the Association. 

 — 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 hav- 

 ing 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 arrange- 

 ment was to enable the thermometers to assume with more rapidity 

 the temperature 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 ris- 

 ing very slowly. The thermometers used were very delicate, 

 the bulbs being cylinders about half an inch long and not more 

 than tVth 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 likelihood not more 

 than may be expected from other accidental causes. 



The observations were taken at short intervals during the ascent, 

 it having been seldom»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 re- 

 corded 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. 



