64 BULLETIN" 801, U. S. DEPAKTMENT OE AGRICULTURE. 



USE AND PRESERVATION OF WOOD. 



The selection of wood for the cotton warehouse is generallj'^ 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 vcarehouse. Southern pine is among the most suitable timber 

 also for warehouses in the ISTortheast and other sections of the coun- 

 try, but in these locations the relative economjr of fire-resistive con- 

 struction should insure its adoption. 



Among the varieties of pine available and suitable for warehouse 

 purposes are those commonljr 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 loug 

 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.^ 



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 qualitj- 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 



^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 tests 

 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. 



