20 BULLETIN 753, U. S. DEPARTMENT OF AGRICULTURE. 
volume of wood but upon its weight. A pound of dry wood of one 
species has about the same number of heat units as a pound of any 
other species; but a cord, assuming the same solid volume of wood in 
each case (90 cubic feet), of basswood, for instance, yields but 12,- 
600,000 British thermal units, while a cord of black locust yields 
26,500,000 British thermal units. As a matter of fact, we can not 
assume the same solid volume in two cords of wood; a loosely piled 
cord of small, round sticks may contain 70 cubic feet or less, while a 
closely piled cord of large split wood may contain over 100 cubic 
feet. If it is locust, the first pile will yield 20,700,000 British thermal 
units; the second, 29,600,000 units. I the first pile is basswood, it 
will have a heating value of but 9,600,000 British thermal units. The 
same cord of wood sawed up and repiled will be less than a cord in 
bulk, though its heating value will not be reduced; thrown loosely 
into a wagon box, it will fill up considerably more than 128 cubic 
feet, but will not give off any more heat. 
It is now the custom in most places to sell hardwoods and soft- 
woods at slightly different prices because of recognized differences 
in heating values. Branch wood is frequently sold at a lower price 
than split body wood, as a result, partly at least, of a hazy recogni- 
tion of the fact that there is less solid wood in a cord of the former. 
Chestnut and hickory, however, are frequently mixed together as 
hardwood, and sold at a given price regardless of whether 90 per cent 
is chestnut, which would give the cord a low heating value, or 
hickory, which would give it a high value. In many places even pine, 
oak, and hickory are indiscriminately thrown together at a uniform 
price, regardless of the proportion of each, so that one man may 
for a given amount of money buy twice as much heat as another. 
The practice prevalent in some sections of selling wood by the load 
has afforded excellent opportunities for profiteering without the 
knowledge of the purchaser. Few people would buy coal by the load 
instead of by the ton, yet a given joad of coal can not vary nearly 
so much in heat value as a load of wood. 
A better way to sell fuel wood would be by weight, which is entir ely 
independent of: species, shape, or size of sticks, or of method of 
piling, and is a very good measure of the fuel value of thoroughly 
seasoned wood. Green wood, of course, varies considerably in water 
content and therefore in fuel value per unit weight, and naturally 
would be sold at a price different from that for dry wood. The 
extreme difference in heat units per pound between green and dry 
wood of any species is approximately 70 per cent of the dry value; a 
pound of green willow, for instance, is worth about one-third as much 
as the same weight of dry wood. Green wood of most of the hard- 
woods commonly used for fuel has about half the heating value of 
dry wood of the same weight. 3 
