HOW THE BURNING OF COAL VITIATES THE ATMOSPHERE.
Every ton of coal, it has been found, which is burned übcs up 300,000 cubic .feet of air and renders it unfit for breathing. Suppose that there were no danger of exhausting our coal supply, and that we had enough to last forever; it would only be a few hundred years at our present rate of increase in coal consumption, until all the atmosphere on the earth's surface would be rendered incapable of sustaining life. However, as has been called to our attention by Prof. Arrhenius, the consumption of coal at present is returning to the stmosphere the carbon dioxide of which it was robbed when the deposits of carbon were stored away in the coal beds during the carboniferous period. The present proportion of carbon dioxide in the air is about one part in 2,500. This would be about doubled, if it were not modified by vegetable life, by the consumption of the present known coal deposits, and it is stated that a doubling of the quantity in the atmosphere would more than double the rate of growth of plant life.