'\IZ INDUSTRIAL USES OF WOOD. 



more than 4-6 years. If the demands were not so con- 

 siderable, none but the most durable oakwood ought to be used. 

 It is, however, more economical to use the wood which is locally 

 most easily procurable, and this is chiefly coniferous, of which 

 liuchwood is most durable, and then resinous Scotch pinewood, 

 but in Germany even sprucewood is sometimes used. Among 

 broad-leaved trees beech is most commonly used, and largely so 

 when shod with steel, as stamping hammers for pounding 

 minerals. 



"With the exception of beams used vertically, dovetailed 

 together in shafts, ladder-wood, and some other pieces, wood for 

 mines is chiefly required in round logs free from bark. Different 

 forms of sawn wood are also in demand for lining shafts, 

 generally in the form of inferior coniferous boards and planks. 

 Wood may be supplied in full-lengthed logs, which the mining 

 carpenter reduces to the required dimensions, or in the form of 

 pit-props, in which the chief bulk of mine timber is com- 

 prised, and which vary from three to eight inches in mid- 

 diameter (not less than 21 inches at the smaller end), and 24 to 

 30 feet long, and even longer. Only about 15 to 20 per cent, 

 of the mining-props are required in pieces measuring 12 to 

 16 inches, mid-diameter. 



[Scotcli pine will yield pit-])rops when 40 years old, and bircli 

 at 25 years, and for British coal-mines over 000,000 tons of Cluster 

 pine arc imported annually from Bordeaux, where it is grown and 

 tapped for resin in the extensive forests of the Landes and fiirondc. 

 -Tk.] 



Wood is put to some other uses where it is subject to similar 

 conditions as wood used in mines ; for instance, well-frames, for 

 which purpose resinous coniferous wood, especially that of 

 larch, black pine, and Scotch pine are suitable ; also in cellars, 

 for bottle-racks, for which oakwood (or iron) is chiefly used. 



Section IV, — Wood i skd in contact with Wateu. 



1. Jir'nhjrs, cCr. 



W^ood used in watercourses and bridges is under very much 



the same circumstances as wood in contact with the ground, 



except that it may be partly or entirely under water. All 



