ON THREE BALLOON ASCENTS IN 1864 AND 1865. 175 



200 feet up to 800 feet, where the temperature was 47° or 5°-3 lower than on 

 the ground : the decline was then less rapid, for on passing through the next 

 800 feet the whole decrease was 2°-l. The temperature then declined rather 

 more rapidly to 35°-l at 3400 feet high ; at 3600 feet it was 34f °, and varied but 

 little from this till 4000 feet had been passed ; it then decreased to 34° at 4600 

 feet, when it suddenly became warm, the temperature increasing to 38|° on 

 passing above 4S00 feet, and to 39^° nearly on reaching 5000 feet, the same 

 temperature having been passed at 2600 feet. The balloon then turned to de- 

 scend, the temperature at first decreasing to 3S°-4 at 4800 feet, being the same 

 as noted on ascending : here a warm current was met with, and the tempera- 

 ture increased rapidly ; when at 4200 feet it was 43°-3, being 9° warmer 

 than was noticed at the same elevation on ascending ; this excess gradually 

 diminished, till at about 2000 feet high the temperature observed during 

 the descent was very nearly the same as. noted, during the ascent; and below 

 this the temperatures were all lower by some -degrees than were recorded at 

 the same elevation during the ascent : these differences seem to be chiefly 

 owing to the presence of cloud situated between 3100 feet and 4100 feet 

 high, or 1000 feet in thickness passed through in ascending, and seen at the 

 same level, but not passed through in descending. The point where the tem- 

 peratures noted were the same ascending and descending was a little below 

 the cloud-plane ; at lower elevations, to the ground, the air was some degrees 

 warmer under the cloud, during the ascent, than in the absence of cloud 

 during the descent. The .effect of the presence of the cloud in this ascent 

 seems to have been to cool the air several degrees ; and this cooling influence 

 seems to have extended for nearly 1000 feet above the cloud, and for 500 

 or 600 feet below ; nearer the earth the presence of the cloud seems to 

 have exercised a warming influence. In the descent it will be seen that the 

 temperature differed very little from 43°, from 4200 feet high to 1000 feet 

 high, the depression' to 41°+ from 3000 feet to 2600 feet being evidently 

 influenced by the passage through the cloud-plane. On ascending again, 

 first haze was passed through, then cloud entered, giving readings differing 

 but little from those met with in the first ascent. On descending to the 

 earth, temperatures a little lower, owing apparently to the diurnal decrease 

 of temperature at these altitudes, were met with, thus far agreeing with those 

 during the first ascent ; and comparison with those during the first descent 

 through a large break in the clouds gives a great deal of information upon 

 the large influence exercised by the presence of cloud. 



In previous Reports a Table (No. IY.) was formed here, showing the 

 decrease of temperature in every 1000 feet ; as no additional information at 

 high elevations is given this year, this Table has not been formed. The 

 residts of Table V. of preceding years are included in Table III. of this year. 



