220 The American Geologist. October, i»9» 
quartz." We shall presently quote another writer giving the 
same testimony. 
I must here digress for a short time from the main line to 
trace a tributary that meets it at this point and whose course 
it is necessary to have in mind in order to develop the argu- 
ment. The geologist, regarding the past history of the globe 
with a critical eye, has long been amazed at the vast masses 
of mineral fuel — coal, petroleum and gas — which he finds ac- 
cumulated in the crust and especially on one horizon. The 
carboniferous system, with its huge stores of free carbon, the 
chief and almost the only resource of the world at present 
for heat and power, and its hope for the future are to him, a 
standing enigma. The botanist assures him that all has been 
extracted from the atmosphere by the agency of green plants, 
under the stimulus of sunshine. No other process is known 
whereby this precious element can be severed from its com- 
pounds and isolated in free form in any appreciable quantity. 
Indeed its separation in the laboratory is a somewhat difficult 
and refined experiment. But this assurance of the botanist 
darkens rather than clears the enigma of the geologist. Re- 
lying with confidence on the botanical principles of his broth- 
er-student, which are confirmed by so many concomitant 
proofs as to be quite unassailable, such as the vegetable struc- 
tures, leaves, stems and fruits found in the coal, he is yet un- 
able to see where these plants obtained so vast a supply of 
carbon. From a careful quantitative study of the atmosphere 
he learns that the sum total of this element therein contained 
is vastly less than that which now lies buried in the earth, so 
that to accumulate another stock of mineral fuel equal to that 
which we are now using so freely and squandering so reck- 
lessly, would be an impossibility. The material is not pres- 
ent in the atmosphere, and what is not there can not be taken 
away. Without troubling you here and now with the calcu- 
lations, I will merely give sufficient results to establish my 
statement and to enable you to follow me with confidence. 
The whole amount of carbon in the air to-day, in the form of 
carbon-dioxide, does not exceed 150 to 200 cubic miles — a 
sufficiently large amount, you are ready to say when you try 
to realize what it expresses. A single cubic mile of coal al- 
most passes comprehension. The world's entire annual con- 
