248 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
the spore cases. More than 2,500 species of fossil plants have left 
their record in the coal measures for us to read to-day. As these 
plants crowded each other in the swamps and died, fermentation and 
decomposition set in with gradual elimination of much of their 
substance as marsh gas and carbon dioxide, but with the proportion 
of carbon in the residue constantly rising. As the land sank or 
rivers rose, clays and sand were deposited upon this residue, which 
gradually was compacted into coal. It is thus possible to trace a 
perfect gradation from wood or peat, through brown coal and 
lignite to bituminous coal, and finally to anthracite and graphite. 
As the result of successive depressions and ‘uplifts of the land, 
the strata in every coal field are repeated many times. There may be 
as many as 100 coal seams, varying in thickness from a fraction of 
an inch to 40 feet or more, and separated by much thicker strata of 
limestone, iron ore, sandstone, and shale. In Nova Scotia the rock 
system comprising the coal measures is 13,000 feet in thickness, and in 
Pennsylvania and West Virginia it is 4,000 feet or more. 
In the intervals between coal strikes we mine in this country about 
600,000,000 tons of coal a year, a quantity which Charles P. Stein- 
metz calculated was sufficient, if used as a building material, to con- 
struct a wall, like the Chinese wall, entirely around the United 
States, while with the chemical energy contained in the next year’s 
coal we could lift this whole stupendous structure into space to a 
height of 200 miles. There are so many other uses for coal, however, 
that neither operation seems worth while at present prices. 
The production and distribution of coal in the United States is 
a business of such vast proportions and complexity that the mere 
maintenance of human relations within the industry involves prob- 
lems so acute and difficult as to lead to frequently recurring crises, 
like the recent anthracite strike, in which, for 165 days, the miners 
received no wages, while the operators incurred enormous losses and 
the public got along as best it could. The basic difficulty in the whole 
coal situation is perhaps the fact that the mine capacity of the 
country is 40 per cent greater than the demand. With the many 
mines and far too many miners it is difficult to insure prosperity 
and employment to all. 
The problems of the coal consumer are of corresponding magni- 
tude, although perhaps less acute. His initial problem is to secure 
an adequate and regular supply of fuel at the lowest reasonable 
price, and his secondary concern is to utilize that fuel to the best 
advantage. Under present conditions the first is largely beyond his 
control, while as regards the second he commonly fails from lack of 
knowledge or from willful disregard of the requirements of good 
practice. The proportion of carbon dioxide in the flue gases of a 
