250 TIMBERS AND THEIR USES 



'mentioned wood which, has been stacked for 

 some time, less moist than green wood,- but 

 more so than kiln-dried wood. It is clear that 

 firewood, to be really efficient, should be seasoned. 

 " Every pound of water combined in the wood 

 requires about 600 units of heat to evaporate 

 it, the unit being the amount of heat necessary 

 to raise 1 lb. of water 1° C. ; so that 100 lbs. 

 of wood with 25 per cent moisture only furnishes 

 about 255,000 units, whilst if kiln-dry, with 2 

 per cent moisture, it would yield 350,000." 



Of our native fuel woods none can compare 

 with Beech, Oak and 'Ash for heat-giving 

 qualities and general utility. Hawthorn, Apple, 

 Yew and Pear are also valuable in this connec- 

 tion ; Hazel too is useful, but difficult to obtain 

 in quantity. Elm is a slow burner, the conifers 

 on account of their resin burn quickly and 

 brightly. Birch is also a rapid-burning wood, 

 but emits comparatively little heat. Plane, 

 WiUow, Poplar and Sycamore are also in more 

 or less request for fuel, but all of them should 

 be properly seasoned to yield satisfactory results ; 

 in fact the only British wood which will burn at 

 all well when green is Ash. The older the wood, 

 the longer it will last and the greater heat it will 

 emit. Though it is hardly likely that timber 

 of the best quality would be used for burning, 

 care should be taken to avoid decayed or dis- 



