The application of nitrogen increased the yield of wheat by 24 bushels an acre--from 14 to 38 bushels--as an average of the last thirty years, following an average increase of 26.3 for the nitrogen applied during the previous thirty years. It is true that the cost of the fertilizers used exceeded the value of the increase in yield; but let us bear in mind that this truth does not destroy the other truth. Prove all things, and hold fast that which is good. It is a good fact that 1218 bushels of wheat were produced by the application of nitrogen to an acre of land during a period of sixty years, over and above the produce of another acre which differed only by not receiving nitrogen; whereas the total produce from an acre of unfertilized land was only 756 bushels during the same sixty years. It is a good fact that the increase alone from the nitrogen applied is more than twice the total yield of the unfertilized land during the last thirty years, and he does well who holds fast this fact. It is also a good fact that as an average of sixty years the yield of barley was increased by 21.6 bushels an acre by nitrogen; that nitrogen increased the yield of hay on permanent meadow land at Rothamsted by 1-1/2 tons an acre as a fifty-year average; and that nitrogen increased the average yield of potatoes by 88 bushels as an average of twenty-six years; while the average of the unfertilized land was only 51 bushels an acre, these increases in barley, bay, and potatoes being obtained over and above the yields where minerals alone were used. Where Is Nitrogen? If nitrogen has such enormous power to increase the yield of our great staple farm crops then we may well inquire, Where is nitrogen, and how can it be secured economically and utilized profitably in practical agriculture? The weight of the atmosphere is 15 pounds to the square inch. This means that a column of air 1 inch square taken to the full height of the terrestrial atmosphere weighs 15 pounds. More than three fourths of the air is nitrogen. Since there are 43,560 square feet in one acre, it follows that the nitrogen in the air above each acre of the earth's surface amounts to 70,000,000 pounds, or nearly 500,000 times the 150 pounds of nitrogen required for a hundred-bushel crop of corn. The leaves of the corn plant are blown about by the wind carrying 75-1/2 per cent of nitrogen, but cannot utilize an ounce of this supply. Many people know that clover and other legumes have power, through the bacteria which inhabit their root tubercles, to feed upon the inexhaustible supply of atmospheric nitrogen which freely enters the pores of the soil; but who knows how much nitrogen is taken from the air by a given crop of clover? Not one in a thousand can answer this question; and meanwhile our continued agricultural and national prosperity depends in large part upon the possibility of wide dissemination and practical application of a quantitative knowledge of the nitrogen problem.