368 REPORT — 1866. 



the time of sunset showed very little or no difference of temperature for a 

 height of nearly half a mile. The question then arose as to whether it was 

 possible that at night the temperature might increase with elevation, and 

 not decrease as always heretofore had been considered, and acted upon when- 

 ever such entered into physical investigation. 



The Committee last year therefore was reappointed with special reference 

 to night observations at any time of the year made within a moderate distance 

 of the earth. To make day observations, in winter and the adjacent 

 months at any hour in the day; in summer to be made in the morning, 

 only the subject of temperature to be considered as of the first importance, 

 with any other of the usual experiments which might be possible. Up to 

 the Meeting at Birmingham twenty-five ascents had been made, of which 

 seventeen had been made iu the months of June, July, August, and September, 

 but not one in May, and mostly during the hours of afternoon. 



§ 1. Insteuments and Apparatus. 

 The instruments were of the same construction as those iised in the previ- 

 ous experiments ; in addition well-made miners' lamps were used to illumi- 

 nate the instruments at night. 



§ 2. Observing Areangesients. 

 The instruments were in all cases placed on suitable framework, attached 

 to the outside of the car, and sufficiently protected from all effects of radiation. 



Circumstances of the Ascents, and General Observations. 



Ascent from Woohvkh Arsenal, October 2, 1SG5. — The first ascent after the 

 Meeting at Birmingham was made on October 2nd. The balloon used was 

 that of Mr. Orton, of BlackwaU. 



When the sun had set for nearly three-quarters of an hour and night had 

 fairly set in, the moon shining brightly, and the sky free from cloud, the 

 balloon left Woolwich Arsenal at 6'' 20"', the temperature at the time being 

 56°. Within three or four minutes a height of 900 feet was reached, and till 

 this time I failed in directing the light of the Davy lamp properly. When I 

 succeeded the temperature was 57° and increasing; on reaching 1200 feet 

 high it had increased to 58°-9 ; we then descended to 900 feet, and the tem- 

 perature decreased to 57°*8 ; on turning to ascend again the temperature in- 

 creased to 59°- G at 1900 feet high, being 3|° warmer than when the earth 

 was left. On descending again the temperature decreased to 57^° at the 

 height of 600 feet, and in the several subsequent ascensions and descensions 

 the temperature increased with elevation, and decreased on approaching the 

 earth. On every occasion the highest temperature was met with at the 

 hio-hest point. This result was remarkable indeed. The difterent degrees of 

 the humidity of the air met with in this ascent are no less remarkable. 

 Considering saturated air as represented by 100, at the commencement of 

 the ascent in the balloon it was 95 ; at Greenwich Observatory it was 84 ; 

 towards the end of the ascent in the balloon it was 85, and at Greenwich was 

 97. The state of things was reversed, and would indicate that the water in 

 the air had fallen. Its amount at the beginning of the ascent was 5| grains 

 in a cubic foot of air, and at the same elevation was 4| grains in the same 

 mass of air at the end of the ascent. 



The readings of the instruments were taken very slowly, owing to the dif- 

 ficulty experienced in directing the light properly. I failed in all magnetic 

 experiments, and indeed in nearly all but those relating to temperature and 



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