The possibilities of such a discovery as this seem almost limitless. Science predicts the exhaustion of nitrogen and consequent failure of the food supply, and science promptly finds a way of making plants draw nitrogen from the boundless supplies of the air. The time may come when every farmer will send for his bottles or cakes of bacteria culture every spring as regularly as he sends for his seed, and when the work of inoculating the soil will be a familiar agricultural process, with discussions in the farmers' papers as to whether two bottles or one is best for a field of sandy loam with a southern exposure. Stranger things have happened. But it must be remembered, also, that the work is in its infancy as yet, and that there are vast unexplored fields and innumerable possibilities yet to fathom. Wonderful as this discovery is, and much as it promises in the future, its efficacy, as soon as it becomes generally known, is certain to be overestimated, as all new discoveries are. Professor Nobbe himself says that it has its own limited serviceability. It will produce a bounteous crop of beans in the pure sand of the sea-shore if (and this is an important if) that sand also contains enough of the mineral substances--phosphorus, potassium, and so on--and if it is kept properly watered. A man with a worn-out farm cannot go ahead blindly and inoculate his soil and expect certain results. He must know the exact disease from which his land is suffering before he applies the remedy. If it is deficient in the phosphates, bacteria cultures will not help it, whereas if it is deficient in nitrogen, bacteria are just what it needs. And so agricultural education must go hand in hand with the introduction of these future preservers of the human race. It is safe to say that by the time there is a serious failure of the earth's soil for lack of nitrogen, science, with this wonderful beginning, will have ready a new system of cultivation, which will gradually, easily, and perfectly take the place of the old. Before leaving this wonderful subject of soil inoculation, a word about Professor Nobbe himself will surely be of interest. I visited his laboratory and saw his experiments. Tharandt, in Saxony, where Professor Nobbe has carried on his investigations for over thirty years, is a little village set picturesquely among the Saxon hills, about half an hour's ride by railroad from the city of Dresden. Here is located the Forest Academy of the Kingdom, with which Professor Nobbe is prominently connected, and here also is the agricultural experiment station of which he is director. He has been for more than forty years the editor of one of the most important scientific publications in Germany; he is chairman of the Imperial Society of Agricultural Station Directors, and he has been the recipient of many honours. We now come to a consideration of the other method--the fixing of nitrogen by machinery: a practical problem for the inventor.