AND THE ACTINIC CONSTITUTION OF THE ATMOSPHERE. 35 



sufficient to cut the two days of observation by an intermediate examination and to 

 discover the intensity of combustion during each one of the intervals. Tims it can 

 easily be seen whether the vessels change at the same rate, after having recovered 

 their "dead time," or whether the vessel which had been insolated (mi the previous 

 day, still progresses more rapidly than its neighbor? 



Exp. — On September 12, 1888, a fine day with a warm sun, and a few cumuli, 

 there were exposed to the sun 4 vessels, Nos. 1, 2, 3, and 4. 

 Vessel 1 was examined 



after 5 hours ; combustion 10 per cent. 

 Vessel 2 



after 9 hours; cninbnstion 18 percent. 

 Vessels 3 and 4 weie put aside and exposed anew on the next day with 

 two new vessels, Nos. 3' and 4'. This day, the 13th, was very fine, with a 

 few cirri in the moiniug. It changed a little for the woi'se towards evening. 

 Vessel 3' was examined 



after 5 hours; combustion 13 per cent. 

 Vessel 3 



after 5 hours; combustion 44 per cent. 

 The difference is considerable and is ceiiainly in part at least due to the 

 suppression of the "dead time" in the vessel which was insolated on the 

 day before. But this again is not all, for during the second half of the 

 day, the insolated vessel kept up a much more I'apid progress than the 

 other, as the following figures clearly show : 

 Vessel 4' examined after 9 hours; combustion 25 per cent. 

 Vessel 4 examined after 9 houi's ; combustion 62 per cent. 

 The acceleration in the solution which had been insolated on the day 

 befoi'e, thus continued throughout the day, and while in the second half 

 of the second day, the new licpiid only showed an increase of 25 — 13 = 

 12 pel- cent in its combustion, the liquid insolated the day befoi-e I'ose 

 from 44 to iV2, iindei'going thus an increase of 18 per cent. 

 It will also be noticed that in the morning this same li(piid had increased 

 from 44— 18 = 26 per cent, while the new liquid experienced a combustion of only 

 13 percent. Here has come in the double effect of suppression of "dead time" 

 and that of the acceleration. The two solutions became a little more nearly equal 

 towards evening, but the insolated solution continued its quicker progress. 



Thus there can be no doubt that the insolation during the previous day 

 continued its effects over the next day and the day after that. But this is not all. 

 One fact, no less curious than the preceiliug, is that the sensitiveness due to the 



