94 
NATURK STUDY. 
mines and left standing about the roots, are the marks of hu¬ 
man endeavor and a mar to the natural beauty, yet no less 
fascinating to the fresh observer. 
To walk the streets of a city where even the public build¬ 
ings are undermined, and are propped by remaining col¬ 
umns of coal, to stand at the mouth of the shaft, as the 
loads of coal are brought forth into the sunlight for the 
first time in ages, and to run over rapidly its transforma¬ 
tion is to be filled with awe. 
Once upon a time in the carboniferous age, before these 
coal measures were formed, the earth was covered again and 
again by ferns and other simple plant organisms, possibly 
woods, and this vegetable matter consolidated through 
pressure and a slow process of oxidation under water 
or other covering sufficient to protect it from the air, 
ai d by frequent changes in earth levels. By experiment, 
it has been shown that of a large number of plants immersed 
in water for two years, the ferns, lycopodiums and pines 
had the greatest power to resist decay, and coal appears to 
be mainly composed of substances belonging to the same 
orders. 
As coal, all former identity of plant life seems to be lost, 
and by analysis the substance is said to contain largely car¬ 
bon with hydrogen, oxygen, nitrogen and some mineral 
matter as lime, iron pyrite and water. 
No living thing was to witness this transformation, but 
without the result and its discovery, the world might stand 
still today for awhile. Perhaps the best estimate of which 
we are capable of the power of natural forces that have been 
at work can be made by the measure of mechanical means 
employed in the excavation of coal, for the forces of cohe¬ 
sion, adhesion and gravity, danger of combustion and flood¬ 
ing from water and difficulty of practical commercial tran¬ 
sit have been overcome in a measure. 
Electrical lighting and haulage will probably come into 
