226 



TIMBER AND TIMBER TREES. [CHAP. 



even in plank, if exposed to a dry current of air, as under 

 such circumstances it is very liable to split with fine deep 

 shakes from the surface. 



Having this serious liability to rend in seasoning 1 , 

 the logs should never be left a week exposed to the 

 influence of drying winds without some kind of protection, 

 for even less than that time is often sufficient to bring 

 about an amount of deterioration which will greatly affect 

 their value. Therefore, to preserve this timber for future 

 use, it should be treated in the same manner as the 

 English common Elm, namely, by immersing it in water ; 

 or, if this cannot be done conveniently, it should be cut 

 into planks of thicknesses which would be available for 



further conversion if required, 

 taking care to store it in a dry, 

 cool place, under cover, but 

 quite free from draught. 



The star-shake, in a mild 

 form, is rather common to this 

 description of timber, but does 

 not usually extend to more than 

 2 or 3 inches from the pith ; 

 there is also another, and rather 

 peculiar defect, consisting of seve- 

 ral complete consecutive circles of the annual layers being 

 softer and more spongy than the natural or healthy wood 

 (Fig. 27). They are darker in colour, and contain much 

 moisture, and are, as pointed out in Chapter VI., p. 34, 

 considered detrimental to the quality, strength, and 

 durability, and consequently, to the value of the tree. 

 The surveyor should, therefore, in selecting this wood 

 take only the logs with a uniform whitish colour for his 

 best work, and leave those which are marked with the 

 dark annular layers upon the ends for inferior purposes. 

 In all other respects the Canada Rock Elm is a safe 



FIG. 27. 



