288 ILLINOIS ACADEMY OF SCIENCE 
ready method of determining them. * * * It is believed that 
the method here worked out (referring to Bulletin No. 3) will 
prove useful in directing attention to certain little understood 
elements of coal, and that with a more complete understanding 
of the material it will prove possible not only to burn it with 
greater economy, but also to adapt various grades to coke 
making, gas producing and other uses from which they are 
now shut out.’” 
So far as the writer is aware, no important progress has 
been made in the solution of the problem stated by Director 
Bain during the ten years which have since elapsed. The study 
of the rate of combustion of some Illinois coals to be pre- 
sented in this paper seems to the writer to have some bearing 
upon the problem. This study is, however, merely tentative 
and suggestive; it is moreover, a comparatively rough method 
directed especially to the study of the domestic use of coal— 
to the use of coal in the ordinary home. A sufficiently large 
proportion of the Illinois output is put to domestic uses, how- 
ever, to justify such a study. The study was suggested by the 
recognition of the fact that for certain domestic uses, such as 
laundry work, a free-burning coal, one from which the avail- 
able heat units may quickly be liberated, is most suitable, while 
for general heating purposes, whether used in furnace, steam, 
or hot-water plant, a coal giving a slow, steady heat is more 
desirable and a slow burning coal is preferable. 
A free-burning coal is highly desirable for use in nearly all 
commercial plants, and especially in steam plants where auto- 
matic stoking is employed or where hand firing can be attended 
to by a fireman in constant attendance. In the case of the 
ordinary heating plant for a dwelling, however, the conditions 
are different. In the majority of cases the heating plant for 
a dwelling, whether it be a furnace, a steam heating plant, or 
a hot water plant, receives attention only at intervals of from 
6 to 12 hours, and often even 24 hours. A steady heat is de- 
sirable at all times. The control of the heat is usually accomp- 
lished during the 6 or 12-hour period by the adjustment of 
the dampers either by hand or means of automatic heat-regu- 
lating devices. 
1. Page 16, Bulletin No. 3, Illinois State Geological Survey, 1906. 
