Many years ago I was asked among others, "What would be the next great discovery of science or invention?" To which I replied, "A supply of nitrogen at low cost." Has not that discovery been made in the recent development of the functions of the bacteria which, living and dying upon the leguminous plants, dissociate the nitrogen of the atmosphere and convert it through the plant to the renovation of the soil? Is not the invention of methods of nitrifying the soil by distributing the germs of bacteria one of the most wonderful discoveries of science ever yet attained? Can any one yet measure the potential of any given area of land in any part of this country in the production of any one of its great crops? That there is a limit may be admitted. Can any one venture to say that any of our average crops yet approach beyond a small fractional measure the true limit of production, whatever it may be, either in cotton, maize, wheat, or any other product of the soil? In this, as in many other developments of the theory of evolution, the factor of mental energy, which is the prime factor in all material production, may have been or is almost wholly ignored. We are ceasing to treat the soil as a mine subject to exhaustion, but we have as yet made only a beginning in treating it as an instrument of production which will for a long period respond in its increasing product in exact ratio to the mental energy which is applied to the cultivation of the land. FOOTNOTE: [9] I have been permitted to review the detailed statements of the accounts of one of the great enterprises which I have called the manufacture of wheat on a large scale on various large farms, separated one from another but under one control, aggregating more than twenty thousand acres, in North Dakota. They are managed mainly from a long distance through agents and foremen, therefore at a relative disadvantage compared to a farmer owning his own land, acting as his own foreman, and saving heavily in expense. Such farmers, making no charge for their own time, are computed to have a cash advantage of one dollar an acre. A large part of this land has been cropped in wheat for twenty-four years, one farm of six thousand acres showing an average in excess of eighteen bushels per acre for the term of seventeen years. The details of the product of other farms are not given, but this may be considered a rule. Of course, this cropping can not be carried on indefinitely. The land is now being allowed to rest, and other crops, such as maize, oats, barley, millet, and timothy, are to some extent being raised in rotation, but not to the extent in which individual wheat farms are now passing into rotation, especially in Minnesota.