e products thus recovered from a ton of
coal multiplies the value of the ton of coal at the mine by at least
thirteen times. The importance of this fact from the conservational
standpoint cannot be too much emphasized. At present over half of the
total coke produced in the United States comes from by-product ovens,
and this proportion will doubtless increase in the future.

BALANCE SHEET SHOWING CONTRAST BETWEEN VALUE OF 1 TON OF BITUMINOUS COAL
AT MINE AND VALUE OF PRODUCTS WHICH IT CONTAINS, BASED ON CONDITIONS
PREVAILING IN 1915.[1]

_Value at _Value at point of
mine 1915_ _Quantity_ production, 1915_
-------------------------------------------------------------------------
1 ton (2,000 pounds) |(1,500 pounds smokeless fuel $5.00[2]
bituminous coal |(10,000 cubic feet gas, at
contains $1.13 | 90c. per 1,000 9.00[3]
|(22 pounds ammonium sulphate at 2.8c. .61
|(2-1/2 gallons benzol, at 30c. .75[4]
|(9 gallons tar, at 2.6c. .23[4]
Total $1.13[5]| $15.59
-------------------------------------------------------------------------
1: Gilbert, Chester G., and Pogue, Joseph E., The energy resources of
the United States--A field for reconstruction: _Bull. 102, U. S.
National Museum_, vol. 1, 1919, p. 11.

2: Figure based upon approximate selling price of anthracite.

3: Figure based upon average price of city gas.

4: These figures would be much higher if an adequate coal products
industry were in existence.

5: This figure shows clearly that lowering the cost of production cannot
be expected to lower the price of coal. Even if the cost of production
were eliminated, the price of coal would merely be a dollar less.

=Classification of coals.= The accurate naming and classification of
different varieties of coal is not an easy matter. The three main
classes,--anthracite, bituminous, and lignite,--have group
characteristics determined by their composition, color, texture, origin,
and uses, and for general purposes these names have reasonably definite
significance. However, there is complete gradation in coal materials
from peat through lignite to bituminous and anthracite coals; many
va