196 J. E. Keeler—Absorption of Radiant Heat 
Time. | Defiec. in ma Time. Defiec. in mm, ! Time. Defiec, in mm. 
| 
4h -2™ 82°4 | 4h §2°5™ | Filled with CQg.|| 55 18™ 56°3 
28 82°4 56°5 5071 19°5 59°3 
29 81-1 575 51°2 20°5 6175 
30 80°9 58°2 50°4 21 Gas nearly out. 
31 81°4 59 51°0 22 63°3 
33 79°8 oe 50°4 22°5 —|appar’tly all out. 
79'9 15 (connected pump 23 69°8 
36°5 79°7 6 : 504 2 73°0 
81:0 vi 50°1 31 73°0 
78-7 12 51°6 32 72:9 
48°5 80°3 13 52°2 34 73°5 
80-2 14 52°9 39 72:8 
51 78°2 16 54°5 40 74:0 
52 784 17 54°6 41 73°5 
If these observations be plotted on paper with abscisse pro- 
portional to the time and ordinates proportional to deflections, 
we obtain a curve showing graphically the absorption of the 
rays from the burner at different times, and hence approxi- 
mately for different thicknesses of CO, From this curve we | 
take at time 4" 57°5™ deflection with air in tube 78:1™; deflec- 
tion with CO, in tube 50°4™™ reduced to time at 4% 57°5™. oe 
This gives an absorption of 35°5 per cent. From a consid- 
eration of all the observations an absorption of 85°8 per cent — 
was taken as that due to the tube when full. 
et us now consider the absorptive media interposing be- 
tween the source of radiation and the bolometer face before the’ 
admission of CO, We may disregard the glass chimney of the 
