INTRODUCTION. 7 
to determine the compressive strength of the coke — or, in other 
words, the height of the furnace burden which the coke will sup- 
port — showed only the worthlessness of such determinations. The 
compressive strength of a given coke made with the same coal ranged 
from about 700 pounds ultimate strength per square inch to over 
2,000 pounds. As a coke with compressive strength of 48 pounds 
will support the burden of any modern furnace, it is evident that 
this test is of little or no practical value, especially as the burden 
borne by the coke may be greatly modified by the action of heat, by 
attrition, and by other factors. The inquiries seem to indicate that 
the yield of coke is increased and the proportion of breeze reduced 
by preliminary crushing. Further experiments are necessary to 
verify these determinations, as well as to indicate the limit of fine- 
ness of such crushing. Fine crushing appears to increase the strength 
of the coke, which is apparently influenced also by the amount and 
distribution of ash. 
More complete coking tests will be carried on with a view to pro- 
curing more conclusive data along the lines above indicated, also 
with a view to determining more accurately the loss of sulphur from 
coal to coke, which varies with the coals and the method of treat- 
ment. These coking tests are being continued at the new plant at 
Denver on beehive ovens with two heights of crown, in order to deter- 
mine the treatment necessary to produce good metallurgical coke 
from the coals mined in the Rocky Mountain region. 
The great need of the immediate future in connection with coking 
experiments is the conduct of such tests in by-product ovens, and it 
is hoped that funds may soon be had which will permit the erection 
and operation of such ovens. 
The cupola tests of coke in 1905 and 1906 were carried on along 
linos fully described in Professional Paper No. 48. The results as 
set forth in the following tables give the details of 170 cupola tests. 
The data concerning record of melt, taken in connection with the 
indications of the source of the coals and the analyses of the corre- 
sponding coke, furnish interesting facts as to the melting ratio of 
iron to. coke, the rate of melting per hour, and the amount of iron 
recovered. Equally interesting is the table giving the chemical 
effect on iron from cupola tests of cokes made from coals mined in 
various States. It is not contemplated that these cupola tests will 
be continued during the fiscal year, in view of the necessity of devot- 
ing the available funds to the study of the coking qualities of western 
coals. 
