AND THE ACTINIC CONSTITUTION OF TIIK ATMOSPHERE. 



47 



and 8.6 c. c, which cori'csjjoiids to combustions of 86 pei' cent and 85 pur cent, 

 respectively. 



It will be seen from ;dl that lias l)een said so far, that the daily actinonietric 

 combustions are (piite as iri'egular in Algeria as in Fiance, and have only a very 

 remote connection with the external aspect of tiie sky and the clearness of the 

 hoi'izou. I have not been so foi-tunate as M. Gessard so far as the weather was 

 concerned. The greater part of the month of August in the Cantal and a part 

 of the month of Se[)tember we had cloudy or I'ainy periods, and during this time 

 observations were impossible. Availing myself of the fact that the method of 

 compai-ison which we employed (-onsists of a comparison of the finest days at the 

 two stations, I shall here report only the figures noted down at Olmet dui'ing the 

 rare times of fine weather. 



Date. 



Solar 

 Combustion. 



Remarks. 



August 27 

 28 

 29 

 3° 

 31 



September 2 



17 

 iS 



19 



20 

 21 



27 

 29 



29 ^ 



42 i 

 41 i 



35 i 

 41 i 

 27 i 

 40 io 

 34 i 



52 i' 

 60 % 



52 ^ 

 28^ 



23 i 



Fine day from beginning to end. 



Fine weather, but rather heavy and stormy. 



A fine day, although rather foggy. 



A fine day, rather stormy. .Some clouds. 



A fine day. Some mist towards 4 o'clock in the west. 



Clear in the morning ; rather foggy in the evening. 



Quite a fine day in spite of g. g. clouds. N. E. wind. 



Cumulus covering \ of sky, all day long. 



Less cumulus than the day before. Finer day. 



A very fine day. 



Rather stormy day. 



A fine day ; few clouds. 



An indifferent day. 



Comparing this list with M. Gessard's we notice in the first place a coincidence 

 between the days of August 27th, 28th, 29th, 30th, and 81st, which were either 

 fine or very fine at Olmet and at 8etif. Now if we compai'e the results of the 

 daily combustion from 8 a.m. till 5 p.m. we find, respectively: 



9, 8, 7, 7, and 7 for Setif ; 

 and 29, 42, 41, 85, and 81 for Olmet. 



If we in like manner compare, leaving out the dates, the combustion on the 

 finest days in Fi'ance and in Algeria, we find again that it decreases with the lati- 

 tude. This is the same conclusion to which we were led, when we compared the 

 obseivations made in France and in Norway, and between the limits of the two 

 stations at Helsiugfors (lat. 60° 19'), and at Setif (lat. 36° 11')- This shows that the 



