AERONAUTIC VOYAGES. 347 



for a long time i-ecorded. This discovery explains how these icy particles may 

 become the nucleus of hailstones of considerable volume, for we readily com- 

 prehend how they may condense around them and solidify the aqueous vapors 

 contained in the atmospheric strata in which they float ; it likewise demonstrates 

 the truth of the hypothesis of Mariotte, who attributed the existence of halos, 

 parhelia, and paraselenes, to crystals of ice suspended in the air. In fine, the 

 presence of a widely-extended cloud of great coldness very well accounts for the 

 sudden changes of temperature which so often and unexpectedly affect our 

 climates. MM. Barral and Bixio, in discussing the meteorological observations 

 made in Europe at the time, including the day preceding and the day following 

 their memorable ascension, were enabled to establish the occurrence of sudden 

 and general accessions of cold, which bore undoubtedly a direct relation to the 

 arrival of the intensely frigorific masses of vapor which were then propagating 

 themselves from the northeast to the southwest. 



VI. — VOYAGES OF JOHN WELSH. 



In July, 1852, the committee of directors of the observatory of Kew, near 

 London, resolved on the execution of a series of aeronautic ascensions with a 

 view to the investigation of the meteorological and physical phenomena which 

 develop themselves in the most elevated regions of tlie terrestrial atmosphere. 

 This resolution was approved by the council of the British Association for the 

 Advancement of Science. Instruments were immediately prepared, consisting 

 of a barometer of Gay Lussac, dry and wet thermometers, an aspirator, a con- 

 densing hygrometer of Regnault, a hygrometer of Daniell, a polariscope and 

 glass tubes to collect the air. The balloon made use of was that of M. Green, 

 who constantly accompanied M. John Welsh, to whom the observations were 

 intrusted ; illuminating gas was employed for inflation. Four ascensions took 

 place, August 17 and 26, October 21, November 10, 1852. In the first two 

 voyages M. Nicklin also accompanied M. Welsh. The place of departure was 

 the garden of Vauxhall. 



In the first ascension, August 17, the expeditionists set forth at 49 minutes 

 after three in the evening, and again touched the earth at 20 minutes after five, 

 23 leagues north of London. They reached the height of 5,947 meters. The 

 lowest pressure they obtained was 364.5 millimeters, and the minimum tem- 

 perature —13°.2. On the earth the barometer indicated 755.1 millimeters, and 

 the thermometer -|-21°.8. A cloud covered the horizon, its inferior limit was 

 reached at about 762 meters, and its superior limit at 3,963 meters. The bal- 

 loon then penetrated into pure air, but at a great distance above there spread a 

 dense cloudy mass. Snow, consisting of star-shaped flakes, fell from time to 

 time on the balloon. 



The second ascension, August 26, commenced at 4 hours 43 minutes in the 

 evening, and terminated at 7 hours 35 minutes; the descent took place 10 

 leagues W.N W. of London. The balloon rose to a height of 6,096 meters, and 

 the lowest temperature observed was —10^.3. On the earth the pressure was 

 760.9 millimeters, and the temperature 4-19.1. A few clouds were suspended 

 in the atmosphere at a height of about 900 meters ; above, the sky was clear 

 and of a bright blue. 



The third ascension took place October 21, at 2 hours 45 minutes; the voy- 

 ao-ers descended at 4 hours 20 minutes, about 12 leagues to the east of London. 

 They ascended only to a height of 3,853 meters ; the least pressure observed 

 was 475.5 millimeters, the lowest temperature —3°. 8. On the earth the ba- 

 rometer marked 759.2 millimeters, the thermometer + 14=.2. Between 254 and 

 853 meters, the balloon encountered detached and irregular clouds ; at about 

 915 meters it entered a continuous bed of cloud, whose upper surface terminated 

 at 1,093 meters. On its emergence from the cloud the balloon projected on its 

 nearly level expanse a shadow surrounded with fringes. The light, directly 



