Appendix 2. 
WOOD PRESERVATION.* 
By Henry Flad, 0. E., Saint Louis, Mo. 
Wood is made up of small fibers, the various forms of which consti- 
tute its cell-structure. Air occupies the cells not filled with sap. 
The woody fiber in all kinds of wood is composed of the same ele- 
ments, and in nearly the same proportions. It consists of 52.4 parts of 
carbon, 5.7 parts of hydrogen, and 41.9 parts of oxygen. 
Differences in the strength of timber are due to differences in struct- 
ure, or in the form and disposition of the fibers. The specific gravity 
of the fiber is about 1.5. 
The sap consists mainly of water, and of the so-called extractive sub- 
stances, such as vegetable glue, gum, gallic acid, coloring matter, sugar, 
albumen, etc. Besides these substances, which are found in greater or 
smaller quantities in almost every kind of sap, that of some kinds of 
wood contains special ingredients 5 oak contains tannin, the coniferous 
woods contain resin, essential oils, etc. 
The quantity of sap contained in wood varies considerably in differ- 
ent kinds and at different seasons of the year. Freshly cut wood con- 
tains from 18 per cent, of sap (in Hornbeam) to 52 per cent, (in Black 
Poplar). The variation of sap at different seasons is illustrated by the 
observation that ash, cut in January, was found to contain 29 per cent, 
of sap, and 39 per cent, when cut in April. 
When wood is thoroughly air dried it still contains from 1G to 20 per 
cent, of water, and when air-dried wood is exposed for a time to a tem- 
* I11 this paper notes signed with, the initials H. C. are to he credited to Mr. Howard 
Constable, C. E., of New York city, who had kindly prepared a separate paper on 
the same subject, but to avoid unnecessary repetitions, his paper has been divided 
and used as foot-notes along with this Report, 
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