*73 
Messrs. Allen and Pepys on the 
were removed from the fire, were exposed in the scale of a de- 
licate balance, in a room where the thermometer was 62°Fah- 
renheit, barometer 30,26. 
Grains. Total Increase, Time. 
6 o’clock P. M. 40 
i past 
- 
4^,7 + ,7 
7 
- 
4T3 + >6 = 1,3 
1 hour. 
i past 
- 
4 1 *® + >3 = 
\\ hours. 
8 
- 
41, 8 +,2 == 1,8 
2 hours. 
The pieces were now spread out on paper after every weigh- 
ing, to expose them 
more completely. 
- past 8 
- 
4 2 >5 + ,7 = 2,5 
2|- hours. 
9 
- 
42,8 + ,3 = 2,8 
3 hours. 
i past 
- 
43 , 1 + >3 = 3 A 
3 t hours ^ 
10 
- 
43^3 + = 3,3 
4 hours. 
i past 
- 
43>4 + A — 3>4 
4|- hours. 
Here it was left 
all night. 
10 A. M. 
- 
4 5 +1,6 = 5 
16 hours* 
4 P. M. 
- 
45 
6 
- 
44 ’5 — ,5 = 4 >5 
24 hours. 
9 
- 
44 > 4 " 4,4 
27 hours. 
Next day. 
i past 8 A. M. 44,9 + ,5 = 4,9 
38^ hours. 
\ past 1 
P. M. 44,7 — ,2 = 4,7 
43|- hours. 
10 
- 
44,5— ,2 = 4,5 
52 hours. 
Hence charcoal seems to act as an hygrometer: its greatest 
increase was 5 grains on 40, or 12^- per cent. And in order to 
ascertain to what the increase of weight was owing, we put 
27,25 grains of charcoal, which hadbeen thus exposed, into a 
small bottle and tube connected with a receiver standing in 
