G7 
perature of -77° F., the quantity of water is reduced to £ or J- of what 
was left in the air-dried wood. 
Note.— The following table exhibits the weight of 1 cubic foot each of different 
kinds of aii-dried wood and the space in a cubic foot, or 1,728 cubic inches, of air- 
dried wood occupied respectively by liber, sap, and air, assuming the specific gravity 
of liber at 1,5. 
Weights of 1 cubic foot. 
Space occupied by fiber, sap, 
and aii\ 
Pounds. 
Per cent, 
of water. 
Woiglit 
of water. 
Weight 
of fibei. 
Fiber. 
Cub. in. 
Sap. 
Cub. in. 
Air. 
Cub. in. 
White Oak 
53.3 
1G 
8.5 
44.8 
830 
1GI 
002 
34. 4 
17 
5.8 
28.0 
530 
101 
1, 037 
26.1 
17 
4.4 
21.0 
400 
125 
1, 203 
814 
Whito Beech 
45.2 
18. 5 
8.4 
3G. 8 
081 
233 
White Elm 
30. 2 
18.5 
1!) 
0.7 
29.5 
540 
18G 
990 
Sweet Gum 
30.0 
7.0 
32.0 
592 
211 
925 
Yellow Poplar 
33.0 
1!). 5 
0.4 
2G.G 
493 
177 
1,058 
Sycamore 
33.4 
20 
0.7 
20.7 
494 
18G 
1, 054 
The weight of water per cubic foot, as given in the third column of the above table, 
and the weight of liber per cubic foot of lumber iu the fourth column, were calculated 
from the observed percentage of water contained in the wood, as given in the second 
column. 
In air-dried wood from one-third to nearly two-thirds of the volume is occupied by 
air, which might be replaced with some liquid if the air were removed, or partly 
renlaced if the air were compressed. [Knapp's " Technology."] 
DECAY OF WOOD. 
The woody fiber by itself does not seem liable to decay ; but the sap 
contained in it under favorable conditions undergoes fermentation, and 
fungi attack and destroy the fiber. 
Fermentation, however, cannot take place except in the presence of 
air, of moisture, and of a temperature above the freezing point (32°), and 
below 150° F. If any one of these conditions is lacking, decay is im- 
possible. 
But if wood is to be exposed to conditions favorable to decay, special 
precautions and means can and should be adopted to prolong its use- 
fulness. The sap being the prime cause of decay, it is plain that timber 
should be cut at a season when it contains the least quantity of it and 
the least amount of organic matter, viz, during winter. 
It is stated on good authority that wood of proper character and age, 
cut during January and then air-dried, resisted decay for fifteen and 
sixteen years ; whereas timber of the same kind, cut at different age and 
season, lasted only four years.* 
*Note. — On this point, see note on page 37. Experience has shown that wood cut 
in August, if properly seasoned, will last as long as that cut in winter. The manner 
of after-treatment will decide mostly for or against the practice of summer cutting. 
If no precautions are taken as to proper seasoning, the winter cutting is decidedly 
preferable. — B. E. F. 
