“The carbonic acid gas produced simply by the breathing of the great human family amounts every year to about 160,000,000,000 cubic meters, which represents 86,270,000,000 kilograms of burnt carbon. Piled up, this carbon would form a mountain one league round at its base and between four hundred and five hundred meters high. So much carbon is required by man to maintain his natural heat. All of us together eat this mountain of carbon in our food and in the course of the year dissipate it all in the air, a breathful at a time; after which we immediately begin the dissipation of another mountain of carbon. How many mountains of carbon, then, since the world was created, must mankind have exhaled into the atmosphere! “We must take account, too, of the animals, which, collectively, those of the land and those of the sea, use up a big mountain of combustible matter. They are much more numerous than we; they inhabit the entire globe, both continents and seas. What a quantity of carbon it must take to sustain the life of our planet! And to think that it all goes forth into the air, as a deadly gas, of which a few breaths would cause death! “Nor is that all. Fermentation, as in grape-juice and rising dough, and putrefaction, as in decaying manure, produce carbonic acid gas. And it needs only a light layer of manure to cause a cultivated field to give forth between one hundred and two hundred cubic meters of carbonic acid gas per day for each hectare. “The wood, coal, and charcoal burnt in our houses, and especially the quantities consumed in the great furnaces of factories—are not they also returned to the atmosphere in the form of harmful gas? Just think of the amount of carbonic acid gas vomited into the atmosphere by a factory furnace into which coal is poured by the carload! Think also of the volcanoes, gigantic natural chimneys which in a single eruption throw up such quantities of gas that furnaces offer no comparison. It is very clear: the atmosphere is constantly receiving carbonic acid gas in torrents that defy computation. And yet animal life has nothing to fear for the present or for the future, since the atmosphere, though continually being poisoned with carbonic acid gas, is at the same time always being purged of it. “And what is the purgative agent commissioned by Providence to maintain the salubrity of the atmosphere? It is vegetation, my friends, vegetation, which feeds on carbonic acid gas to prevent our perishing and turns it into the bread of life for our sustenance. This deadly gas, which absorbs into itself all sorts of putrefaction, is the choicest of nourishment for plant-life; and thus out of the bosom of death the blade of grass builds up new life.