USE OF THE WOOD. 21 



sizes, these regained more than half the water and underwent over half the total swelling during 

 tlie first ten days after leaving the kiln (see tig. 4). P^ven in this less than air dry wood the 

 changes in weight far excel the changes iu volume (sum of radial and tangential swelling), and, 

 therefore, the specific gravity even at this low per cent of moisture was decreased by drying and 

 increased by subsequent absorption of moisture. Immersion and, still more readily, boiling cause 

 the wood to return to its original size, but temperatures even above the boiling point do not 

 prevent the wood from " working," or shrinking and swelling. 



In fig. -i are represented the results of experiments on the rate of loss of water iu the dry 

 kiln and the reabsorption of water iu the air. The wood used was of Loblolly and Shortleaf Pine 

 kept on a shelf in an ordinarj^ room before and after kiln drying. The measurements were made 

 with caliper. 



EFFECT OF "BOXINCt,'' OR "BLEEDING-." 



"Bleeding" pine trees for their resin, to which chiefly Longleaf and Cuban Pine are subjected, 

 has generally been regarded as injurious to the timber. Both durability and strength, it was 

 claimed, were impaired by this process, and in the specifications of many architects and large con- 

 sumers, such as railway companies, "bled" timber was excluded. Since the utilization of resin is 

 one of the leading industries of the South, and siuce the process affects several milUons of dollars' 

 worth of timber every year, a special investigation involving mechanical tests, physical and chem- 

 ical analyses of the wood of bled and unbled trees from the same locality were carried out by this 

 division. The results prove conclusively (1) that bled timber is as strong as unbled if of the same 

 weight; (2) that the weight and shrinkage of tlie wood is not affected by bleeding; (3) that bled 

 trees contain practically neither more nor less resin that unbled trees, the loss of resin referring 

 only to the sapwood, and therefore the durability is not affected by the bleeding process. 



The following table shows the remarkable numerical similarity between the average results 

 for three groups of trees, the higlier values of the bled material being readily explained by the 

 difl'ereuce iu weight: 



Specific 

 jei^Uof 



Unboxeti trees 



Boxed ami rec:eutly abaudoned .. 

 Boxed aud abaudoned five years. 



Bending Compression 1 



stiengtii sirengih 



per sq ua re per square 



inch. I inch. ' 



The amount of resin in the wood varies greatly, aud trees growing side by side differ within 

 very wide limits. Sapwood contains but little resin (1 to i per cent), even in those trees in which 

 the heartwood contains abundance. In the heartwood the resiu forms from 5 to 24 per cent of the 

 dry weight (of which about one-sixth is turpentine), aud can not be removed by bleeding, so that 

 its quantity remains unaffected by tlie process. 



Bled timber, then, is as useful for all purposes as unbled. 



U8E OF THE WOOD. 



In its use the wood of all four species is iiuicli alike. The coarse-grained, heavy, resinous 

 forms are especially suited for timbers and ilimcnsion stuff; while the fine-grained wood, whatever 

 species it may belong to, is used for a unnt \:ii iity of jjurposes. 



At present distinction is but rarely made in the species and in their use; all four species are 

 used much alike, although differentiation is very desirable on account of the difference in quality. 

 Formerly these pines, except for local use, were mostly cut or hewn into timbers, but especially 

 since the use of dry kilns has become general and the .simple oil finish has displaced the unsightly 

 painting and "graining" of wood. Southern iiine is cut into every form and grade of lumber, 

 Xevertheless, a large proportion of the total cut is still being sawed to order in sizes above G 

 by inches aud lengths above 20 feet for timbers, for which the Longleaf and Cuban Pine furnish 

 ideal material. The resinous condition of these two pines make them also desirable tor railway- 

 ties of lasting quality. 



