OLAISHEK'S BALLOOIT ASCENTS.] 



METEOROLOGY. 



1183 



rose more rapidly, each instant opening to us ravines of 

 wonderful extent, and presenting elsewhere a mighty sea 

 of cloud. Here there were shining masses in mountain 

 chains, some rising perpendicularly from the plains, dark 

 on one side, and silvery and bright on the other, with 

 summits of dazzling whiteness : some there were of a 

 pyramidal form ; a large portion andulatory ; and, in the 

 horizon, Alpine ranges bounded the view. A height of 

 nearly three miles was reached." 



In reference to the ascent of September 1, Mr. Glaisher 

 remarks "When at the height of three-quarters of a 

 mile over London, the whole course of the river Thames 

 was visible from its mouth ; and parallel to it, and 

 bounded by its banks, a cloud or fog-bank extended the 

 whole distance, following all its sinuosities. For half-an- 

 hour before its descent, near Woking, in Surrey, the 

 balloon was under one stratum of cloud, and above 

 another : the upper surface of the latter was remarked 

 as bluish white ; the middle portion the pure white of the 

 cumulus ; and the lower surface a blackish white, and 

 from it, rain was falling on the earth. The balloon 

 descended to a height of 1,300 feet, but was still above 

 the clouds. It was afterwards learnt that rain had been 

 falling from these clouds all the afternoon." 



In the following year (1803), Mr. Glaisher made 

 fifteen ascents ; and the results obtained agree, in the 

 main, with those already detailed. The weather, during 

 the summer, was generally calm, and comparatively little 

 raiu fell for some months. It will be unnecessary for us 

 to present, in a tabular form, the results obtained ; but 

 we shall conclude our notice of the ascents by giving 

 some of the most interesting particulars of the last, which 

 was made on September 28. The object in this one was 

 chiefly to observe the effect due to the influence (if any) 

 of the autumnal equinox on atmospheric phenomena. 



The balloon rose from the earth at 7h. 43m. ; in two 

 minutes afterwards it was at a height of 500 feet ; in 

 four minutes, at 1,000 feet ; in nine minutes, at 2,000 

 feet ; 2 miles high at 8h. 30m. ; . 2J miles at from 

 8h. 45m. to 9h. 8u. ; 2J miles from 9h. 15m. to 

 Oh. 23m. ; and at IH miles, the highest point, at 9h. 

 33m. : it then descended to 2J miles at 9h. 52m. ; 2 

 miles at Oh. 59m. ; 2 miles at lOh. 4m. ; 1 .'. mile at 

 lOh. 9m. ; 1 mile at lOh. 13m. ; 3,000 feet at I Oh. 

 15im. ; ],000 feet at lOh. 23m. ; reaching the earth at 

 lOfi. 30m. The temperature of the air at 7 o'clock was 

 43, and it became 48 when the balloon left the ground 

 at 7h. 43m. ; at 1,000 feet elevation it was 45"; at 3,000 

 feet, 40 3 ; at 5,200 feet, 34; at 8,000 feet, 27; at 

 10,600 feet, 21 ; and at 13,000 feet, 12. The tempera- 

 ture varied irregularly with the rising sun, increasing to 

 16 at a height a little above 2i mile*. On descending, 

 the temperature, which varied from 7 to 15 at the 

 height of 2jf miles, gradually increased to 35 at 5,000 

 feet ; 40 at 3,000 feet ; 53 at 1,000 feet ; and the same 

 amount was noticed on reaching the ground. 



The temperature of the dew-point* was 44 on the 

 ground ; 3.V at 2,000 feet high ; 25 at 5,200 feot ; 20 

 at 13,000 feet; ranging, at this level, between 20 and 

 12 ; sometimes being at the same temperature as that of 

 the air, and, therefore, indicating complete saturation in 

 some places. Above this level, the dew-point decreased 

 to 10 below zero, approaching more nearly to saturation 

 than had been noticed, at that height, in previous 

 ascents. On descending, the dew-point rose till it at- 

 tained 46, which was the temperature at which it was 

 produced at the time of reaching the earth. On the 

 ground, the air contained 3} grains of aqueous vapour in 

 the cubic foot ; at 2,000 feet elevation there were 2i 

 grains ; at 5,200 feet, 1 J grain ; and at the height of 

 17,000 feet, there was less than half a grain in a cubic 

 foot. Presuming the greatest amount of moisture which 

 could be present at the then temperature of the air, to be 

 divided into 100 parts, it would have been, on the ground, 

 and up to a height of 1,000 feet, equal to 90 parts ; at 

 5,200 feet, 72 ; and varied, between 70 and 100, up to the 

 highest point reached. 



In comparing the decrements of temperature during i 



Set ante, p. 1HO. I 



the ascent, and the increments as the descent was 

 effected, it will be evident that no regularity could be 

 noticed. If the results, again, are compared with those 

 given at page 1182, the discrepancy is still more apparent. 

 But this might have been expected, from the circum- 

 stances under which the observations were made. The 

 ground was below the ordinary temperature at the early 

 hour of starting ; for, immediately the sun rose, the 

 temperature was also raised. Of course, during the 

 ascent, every stratum of air passed through would be 

 similarly affected by the absorption of the heating 

 solar rays ; and hence any observations would be 

 incomparable, in a practical point of view, with others 

 preceding or following them. Instead, therefore, of 

 the temperature decreasing, in a regular ratio, as a 

 greater elevation was attained, the solar influence quite 

 prevented such a result ; and, in the descent, similar 

 irregularities would be met with. Comparing the 

 observations up to one mile elevation, we have a tem- 

 perature at 



Ascent. Descent. 



feet . of . 41 . of . 53 

 1,000 . . 45 . . 53 

 3,000 . . 40 . . 40 



5,200 34 . . 35 



Whence it would appear that the influence of local 

 causes, such as terrestrial radiation, convection of heat 

 upward from the surface of the earth, &c., greatly 

 affected all the observations made up to a height of 

 about one mile a result similar to that mentioned at 

 page 1182. 



Although, for purely scientific purposes, these ob- 

 servations afford no certain data, we may yet gather 

 valuable hints from them in a sanitary point of view. 

 It is plainly evident that our atmosphere will be con- 

 siderably and unequally affected at times, with respect to 

 its purity, if it be so in regard to its temperature ; because 

 a normal atmosphere, acted on by tho simple physical 

 laws of pressure and expansion alone, would certainly 

 decrease in its sensible heat in definite ratios depending 

 on the altitude. But, from actual observations in^this 

 island, we find that there exists an extensive strata, 

 just touching the earth's surface, which cannot bo proved 

 to obey tliis law in an equable manner ; and this seeming 

 exception arises solely because tho effects are masked by 

 accidental, and, therefore, local causes. Mr. Glaisher 

 has, more than once, noticed tho smoke, etc., from largo 

 towns (especially London), to reach a mile in height ; 

 just, in fact, the elevation beneath which the law of 

 the temperature, being in the inverse ratio of the altitude, 

 appears to be stopped in its action. From the numerous 

 observations made, it has also been shown, that the 

 stratum of air, within a mile over the earth, is that most 

 readily affected by storms a result which wo should 

 fully expect, from the abnormal state into which it is 

 thrown by the variety of disturbing causes to which its 

 lower mass is subject. 



Let us, for a moment, direct attention to the various 

 affections to which tho atmosphere existing over large 

 towns is liable. Thousands of fires in private dwellings ; 

 furnaces in the various manufactories ; heat from the 

 bodies of the inhabitants ; radiation of previously 

 absorbed solar heat, from the materials of the houses, 

 paved roads, <tc., <fec. ; all tend to cause an enormous 

 up-draught of heated air, which rises as if produced from 

 an immense furnace. A spectator, situated at a short 

 distance Trom any of our largo towns (especially London), 

 if on an elevated position, and in the absence of all 

 wind, will observe an immense body of smoke, &c., 

 rising vertically, and spreading itself, like a canopy of 

 darkness, over the under-lying city. This suioke, or 

 vapour, embodies every volatile impurity produced by 

 all possible causes ; and so long as it has a higher tem- 

 perature than tho atmosphere, it remains suspended 

 over-head. If a purely normal atmosphere, uninfluenced 

 by external disturbing causes, were perpetually sur- 

 rounding such a district, every gas, and particle, of 

 greater specific gravity than itself, would, on gaining the 

 temperature of the air, be precipitated on to the place 



