THE CARBONIFEROUS AGE. 
49 
Coal is a great blessing to man. It furnishes him 
tire for warmth and for steam-power, and gas for 
lighting. Millions of tons are mined and consumed 
every year. In 1900 Great Britain mined two hun¬ 
dred and fifty-two million tons, and the United States 
two hundred and seventy million tons. All the coal 
mined in the world during that year amounted to 
Pig. 27.—Vegetable structure in coal as seen with a microscope. 
eight hundred and forty-five million tons. It is 
claimed that if coal-mining continues to increase as it 
has done during the past ten years. Great Britain will 
exhaust her mines in about a hundred years. 
When we say that coal is a great blessing to man, 
we must not forget that there are few blessings with- 
