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APPENDIX III. 



NOTE ON THE PREPARATION OF WOOD AND THE MANUFACTURE 



OF RAILWAY SLEEPERS. 



I. SEASONING OF TIMBER. 



Trees contain 20 to 60 per cent, of water, 15 to 20 per cent, of which is permanently 

 retained by timber dried at ordinary temperatures, and constitutes the "hygrometric water." 

 Seasoning effects the removal of the superfluous water, and may be hastened by artificial 

 means. In natural seasoning, timber loses one-fifth to one-seventh of its weight ; some- 

 times as much as one-third before it is perfectly dry. The time required for thorough 

 seasoning may vary from 3 years with sawn resinous woods, or 4 years with hardwoods 

 4 inches thick, to 10 years with hardwood logs 2 feet thick. Timber shrinks during 

 seasoning, and much more in a direction transverse to the fibres, especially along the 

 annual rings, than longitudinally. A plank of Oak or Yellowwood may shrink in width 

 one-twelfth, and one of Pine or Stinkwood one-thirtieth to one-fortieth. It is this 

 shrinkage that causes the heart shakes (radial) and cup shakes (along the rings) which 

 often detract so much from the value of timber. 



Girdling is sometimes practised to hasten seasoning, particularly with Teak trees in 

 India; it consists in cutting a ring through the bark and the sapwood of a tree. 

 After several days or weeks, or even months, according to the species, the tree dies if the 

 sapwood has been completely severed, and it is then allowed to stand till the wood is 

 dry. Teak trees in Burmah are left standing for one or two or three years, in order to get 

 the timber sufficiently dry to float. Girdling has many disadvantages : (a) the heart 

 shake is increased in dead trees left standing exposed to the wind ; (6) the wood becomes 

 brittle and liable to be shattered in the felling ; (c) the increased hardness of the wood 

 renders the cutting up more laborious ; (d) the risks from fires are increased ; (e) the risk of 

 damage from wood-boring insects is great ; (/) it is inapplicable to some kinds of wood, 

 which decay unless they are converted into lumber soon after felling ; (g) the delay, 

 of 2 or 3 years, required may often prove inconvenient. Against these drawbacks : (a) 

 the weight of the wood may be reduced by one-fifth, and the cost of transport lessened 

 in proportion ; (6) woods heavier than water when green, may become sufficiently dry to 

 be floated along streams ; (c) the durability of some kinds of woods is said to be increased 

 by the process but it is doubtful whether the durability becomes greater than when 

 timber is carefully seasoned in the ordinary manner. 



A preferable method consists in not crowning the felled trees before the foliage is 

 dry; while green, the leaves assist in removing the superfluous sap. Deciduous trees 

 are sometimes felled when the new leaves come out ; these open out completely after 

 and draw off a proportion of the sap. 



The barking of logs promotes very powerfully their dessication. Uhr, comparing the 

 loss of weight of oak logs, barked and unbarked, found that four months after felling, the 

 barked logs had lost 39'62 per cent of their weight, while the unbarked logs had lost only 

 0*98 per cent. Another advantage resulting from the barking or squaring of logs is that 

 timber so treated becomes less readily attacked by xylophagous insects. 



The steeping of logs in water, for a fortnight or more, soon after felling, is another 

 means of extracting a portion of the sap, and accelerating the seasoning. 



Logs should generally be barked or squared within a fortnight of the time of felling ; 

 and the sooner removed from the forest the better, but they should be kept sheltered from 

 the action of the siin. Squared timber is less liable to split than round timber ; sawn 



