Timbers. 



220 



[March, 1910. 



wood have these different kinds of 

 cells arranged or grouped together in 

 such a way as to form the annular 

 rings which are so distiuct on the cross 

 section of most lumber and give the 

 beautiful watered grain to longitudinal 

 sections. 



When the growth of the tree begins 

 in the spring or at the beginning of the 

 wet season in most tropical countries, 

 there is a great demand for water in 

 the crown where the multitudes of new 

 leaves and twigs are forming, hence a 

 new layer of large loose thin-walled 

 cells is rapidly built; when the demand 

 for crude sap is not so gteat, and 

 when there is plenty of digested food 

 to supply building material, the cells 

 formed are narrow and thick walled, 

 thus the latter growth of each season is 

 heavier, stronger and darker in colour 

 than the earlier growth. As long as 

 the tree is in good condition, distinct 

 rings are left, one for each year, which 

 the foresters and lumbermen make use 

 of in determining the age of the trees of 

 the forest. Fire or insects or any- 

 thing of the kind damaging one side 

 of the tree will often be the cause of 

 incomplete annular rings. Seasons of 

 drought leave narrow and indistinct 

 rings that prove correct records of 

 those dry years throughout the exist- 

 ence of the trees. These accurate re- 

 cords were very valuable to the parties 

 who determined the great age of the 

 grand Sequoias of California. 



Other markings, peeular and interest- 

 ing, and that have much to do with the 

 finishing of some species of wood, are 

 the dappels of thin plates of cells 

 belonging to the Meddulary rays. 

 These lines of cells run from the pith in 

 the centre to the bark as longitudinal 

 layers. Their function is to strengthen 

 and bind the annual layers. Though 

 they are present in most tree stems, 

 they seldom appear more than faint 

 lines radiating from the centre of cross 

 sections. In oak they are very con- 

 spicuous and add g^eat value to it. To 

 get oak boards well marked with these 

 medullary rays, the logs are cut into 

 quarters, each quarter being ripped up 

 into boards with their cutting plane 

 oblique to the quartering cuts (or as 

 near as possible along the lines of rays). 

 This brings the surfaces of the boards 

 nearer to the radiating medullary rays 

 of the log, thus giving many of the 

 dapples on each surface. This quarter 

 cutting greatly increases the cost of the 

 lumber because of the waste, but at the 

 same time increases its strength and 

 enhances its beauty. Trees of the forest 

 that yield the most handsome lumber 



with a beautiful and well marked finish 

 are those which have plenty of room 

 for growth, which are exposed to winds 

 that cause them to bend and toss, and 

 which have ample light and space for 

 development. 



The composition of wood is of im 

 portance to the wood finisher. It is 

 briefly but well pxplained in " A Primer 

 of Forestry," Bulletin No. 24 of the 

 Division of Forestry, U. S. Department 

 of Agriculture. 



" Wood is made up chiefly of carbon, 

 oxygen and hydrogen. When perfectly 

 dry, about half its weight is carbon and 

 half oxygen and hydrogen, in almost 

 the same proportion as in water. It 

 contains also about one part in one 

 hundred by weight of earthy consti- 

 tuents. The nitrogen and water taken 

 up by the roots were originally in the 

 air before they reached the ground , it is 

 true, therefore, that when wood is burn- 

 ed, those parts of it which come from 

 the air go back into it in the form of 

 gas, while those which come from the 

 soil remain behind in the form of ashes,' 



The cell structure of most woods, as 

 left by the smoothing tools of the work- 

 man, is so open that it is difficult to get 

 a finished surface without using con- 

 siderable expensive polish or varnish, 

 which would have to be applied in thin 

 coats with considerable time for each 

 to become hard. This difficulty is over- 

 come by the use of a filler ; the name 

 implies its object. A cheap, durable 

 mixture is rubbed into the openings of 

 the wood forming a body, or foundation 

 upon which the finish is to be placed. 

 Very hard, close grained woods, as olive, 

 lignum vitae and some species of 

 eucalyptus do not need the filler. 



Wood filler for many kinds of woods 

 may be purchased ready for use. Cheap 

 varnish is sometimes used as a filler, and 

 shellac cut with alcohol makes one of 

 the best for work where the pores are 

 not too large. Large cracks may be 

 filled with a composition consisting of 

 rosin and beeswax. Two applications of 

 filler, if well applied, are usually satis- 

 factory for any kind of finish. (The 

 second coat should not be put on until 

 about 36 or 48 hours after the first.) 

 Too much of a single coat is apt to 

 shrink away into the wood. Equal 

 parts of Japan drier and boiled linseed 

 oil, thoroughly mixed, with a body of 

 corn starch to form a thick putty-like 

 paste, thinned down to the desired 

 liquid with turpentine, makes a filler 

 that is suitable for most woods. Instead 

 of corn starch, some earthy material as 

 plaster of paris, whiting or pumice stone 



