54 BULLETIN 801, XT. S. DEPARTMENT OP AGRICULTURE. 
USE AND PRESERVATION OF WOOD. 
The selection of wood for the cotton warehouse is generally re- 
stricted to Southern pine, as the majority of cotton warehouses are 
located in the southern part of the country where that wood pre- 
dominates. This natural limitation is not a disadvantage as the sev- 
eral species of pine meet almost every need for timber construction 
of the warehouse. Southern pine is among the most suitable timber 
also for warehouses in the Northeast and other sections of the coun- 
try, but in these locations the relative economy of fire-resistive con- 
struction should insure its adoption. 
Among the varieties of pine available and suitable for warehouse 
purposes are those commonly known as longleaf and shortleaf, there 
being several varieties with more or less distinct characteristics 
which are very roughly but commonly spoken of under these terms. 
The longleaf pine is superior for most structural purposes to the 
other varieties. Some of the chief advantageous qualities that have 
been accredited to longleaf pine are due to the characteristic long 
timbers comparatively free from defects. However, it is so nearly 
impossible (and certainly impracticable) to identify the different 
varieties of pine after they are sawed into timbers that great dis- 
satisfaction has arisen over the specification of "longleaf pine" and 
this method is giving place to the " density method " of grading 
Southern yellow pine. 1 
Economy in the quality of timber used for the cotton warehouse 
generally should be affected by the use of " dense " timbers for beams 
and "sound" timbers for posts, all free from serious defects, and 
acceptance of lumber of a somewhat lower quality for the heavy 
floor and roof planking. The usual load is so light that the thick- 
ness required to affect slow-burning makes defects such as sound 
1 The basic principle of this method is that pine timbers having a large 
percentage of summer wood in proportion to spring wood — as shown on the 
end section by the dark-colored rings being close together or relatively wide 
or both — is much stronger than timbers of rapid growth as indicated by a 
small ratio for the area of dark rings. Even that variety of pine generally 
known as " loblolly " shows a fair degree of strength when dense timbers 
are selected. The U. S. Forest Service has conducted very complete te<ts 
for determining a fair method of arriving at the relative structural merits 
of Southern yellow pine. The report of the Forest Service was adopted by 
the Southern Pine Association in January, 1915. and by the American Society 
for Testing Materials in August, 1915. Now specifications may be based upon 
the density, which is indicative of the unit strength for perfect timbers, and 
upon the location as well as the kind and size of defects. The recommenda- 
tions of the Forest Service as to density and defects and a discussion of the 
subject is contained in convenient form in an illustrated pamphlet issued 
by the Southern Pine Association. Very complete data on tests of wood is 
contained in Bulletin No. 556 of U. S. Department of Agriculture: Mechanical 
Properties of Woods Grown in the United States, 1917. 
