BEST TIME FOR CUTTING TIMBER. 
339 
In another point of view, the amount of water is important to be known, for the dif¬ 
ference between taking green and dry wood to market, as well as in its consuming', is very 
great; and so also, as ample experience proves, there is a material difference in burning 
green and dry wood. The quantity of water in the wood varies from 20 to 50 per centum, 
and probably the average amount will not differ much from 35 or 40 per centum. This 
water is not only of no use to the fire-wood, but it is prejudicial, as it must be dissipated 
by heat, in which act heat or caloric becomes latent and lost, especially if the wood is 
consumed upon a hearth or in a stove. 
In addition to the effect of water in diminishing the combustibility of wood, the alkalies 
have also considerable influence of this kind. Elm, which is a potash wood, burns with 
less freedom than hickory, which contains much lime. It is, however, possible that the 
size of the pores of wood may modify its combustibility. Black oak is a notable instance 
of a slow and drizzling combustion : the pores are large and numerous, from which the 
watery sap continually oozes. 
