254 WOODS OF COMMERCE. 



to its fibres. Oak timber is apt to be affected by star and cup 

 shakes, especially in certain districts ; and, though it can be 

 readily seasoned, it is very liable to warp and shrink during the 

 process. 



When Oak was largely in use in our Royal dockyards the 

 rules as to specifications were that only logs would be accepted 

 10 ft. or more in length that would side 9 inches and upwards in 

 proportion to their length ; and that each piece was measured for 

 contents by calliper measurement as far as its spire (or top-end) 

 " will hold 12 inches in diameter." It was then found by experi- 

 ence that 30 inches calliper will yield sided timber of about 21 

 inches, 24 inches calliper 18 J in the side, or on an average a 

 "siding" of about two-thirds of the calliper measurement. For 

 fencing or staves, Oak splits easily, with a moderately smooth 

 surface ; and, for ornamental purposes, it is susceptible of a high 

 polish. 



The sapwood is very liable to insect-attack and cannot be 

 termed durable ; but the heart, whether under ground, under 

 water, or exposed to alternations of drought and damp, is re- 

 markably so, few woods changing so little when once seasoned. 

 The " life " of a railway-sleeper of young Oak is stated to be from 

 7 to 10 years if not treated with any preservative, or 16 years if 

 treated with zinc-chloride. The piles of Old London Bridge 

 taken up in 1827, sound after six and a half centuries' use, are a 

 striking instance of these lasting qualities ; whilst the " Bog-oak " 

 blackened by the action of the iron-salts in peat-mosses on the 

 tannin it contains a natural ink remains sound after far longer 

 periods. The durability of Oak timber is undoubtedly affected 

 by the time of year at which it is felled, the best season being 

 winter, when there is least water and sap or fermentable matter 

 in the wood. The greater amount of tannin in the bark and the 

 greater ease in stripping it in the spring have, however, often led 

 to the trees being felled at that time. Incipient decay often 

 shows itself in the heartwood of ancient oak trees as "foxiness," 

 a warm deepening of the colour that actually enhances the value 

 of the wood for some ornamental purposes. 



