duced one and one half tons were lost." That is due to our carelessness: to our limited knowledge is due the waste of over ninety per cent, of the energy of the coal burned under our steam boilers but not given out by the connected engine.
In the preparation of blast-furnace coke from coal by far the greater part of the by-products are not saved. Thus Bogart states that in 1907 62,000,000 tons of coal were coked, but only 14 per cent, in such a way as to recover the by-products; that by this process there were wasted 148 billion cubic feet of gas worth 22 million dollars, 450,000 tons of ammonium sulphate of as great value and tar to the value of nine million dollars, and that the gases lost annually in the coke industry have a calorific power equal to four billion kilowatts, or three billion horse power. As to natural gas, the United States Geological Survey accepts the judgment of State Geologist White, of West Virginia, that not less than one billion feet are wasted daily. "This," he says, "equals the annual consumption of natural gas reported for 1907. This waste should furnish light for half the urban population of the United States."
Of our forests thousands of acres are destroyed each year by fire and, in addition, a large part of the cut is left to rot as stumps, tops and branches, only the best part of the trees being used. The story of the soil has been similar; we have raised crop after crop from it, robbing it of the elements which the plant must have for the building of its tissues. Of all except three of these the average soil has a sufficiency, but potassium, phosphoric acid and combined nitrogen are frequently deficient. Inasmuch as plants can not thrive unless all their needs are provided for, it follows that these must be supplied if they are in any degree lacking. At present we are drawing heavily upon our resources of all three. Potassium, in early days derived from wood ashes, is now being taken from the immense deposits at Stassfurt; but it is a well-known fact that recently the German government has taken measures to largely prevent the exportation of their output. Phosphoric acid has been furnished by our mineral phosphates, which have been recklessly drawn upon for domestic use as well as for exportation until the supply is sadly impaired.
Some species of plants can utilize the free nitrogen of the atmosphere, but most of them can assimilate this necessary element only when it has been previously combined with others in such compounds as saltpeter, ammonium salts or organic matters. One of these, Peruvian guano, has already disappeared. The great deposits of sodium nitrate—Chile saltpeter—on the west coast of South America are being fast removed. Nearly one hundred million dollars' worth are shipped in a year and thirty to forty years will probably see the last of this supply. No other known deposits can replace it. The ammonium salts from