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found in England, France. Germany, Spain, the 1slands of Caribbean Sea, Canada, different parts of the United States, and elsewhere, and the already visible. supply, that which has been discovered in the present century, is sufficient for the agriculture of untold thousands of years to come.
For the potash there was for a time no adequate promise. The soapmaker long ago outbid the farmer for the potash of wood ashes; that of saltpeter is very limited in quantity, and wanted for making gunpowder, salting meat, and other purposes. A process was invented for obtaining potash from sea water, which contains a very minute percentage, but the cost of extraction was too great to make it feasible. But some years ago it was discovered that this costly process of evaporation had been carried out on an immense scale, in past geologic time, over an area of some sixty square miles, in the region of Staasfurth, in Germany, and that in this almost inexhaustible bed of sea salt, the potash compounds were on the top. The use of the German potash salts speedily became common in European agriculture and has extended to the United States and to the coffee fields of Brazil and Ceylon. The results have been remarkable. Muriate of potash, mined and refined in Germany, brought to this country, and applied at the rate of one hundred and fifty pounds, costing $3.50, per acre, on the wornout soil of a farm within a mile and a half from where I am now writing, has made the difference between corn so poor as to be hardly worth the husking and a crop of sixty bushels per acre of the finest shelled corn and a most excellent growth of stalks. Even if in the far distant future the Staasfurth potash mines should be exhausted, it is by no means improbable that others may be found. It is evident, then, that we need not be troubled about the phosphoric acid or the potash.
With the nitrogen the case has, until lately, been somewhat different. Although four-fifths of the air are made up of this element, and over every acre of land there are hundreds of tons of it, crops often fail for lack of it. The prevailing doctrine has been that plants do not avail themselves of the nitrogen of the
air to any extent, but are dependent solely on that which has been accumulated in the soil in past time or is supplied as manure. The scientific interest of the subject and its incalculable importance have made the question of the acquisition of atmospheric nitrogen by plants one of the hardest fought in the annals of biological and agricultural chemistry.
Inat plants should be without this power appears strange, and many observed facts in agricultural practice imply, very decidedly, that leguminous plants, such as clover, vetch, beans, and peas, somehow succeed in getting hold of the free nitrogen of the air and using it for their growth. But the experiments of the most noted investigators have seemed to bring positive evidence to the contrary, and the prevalent doctrine has been that atmospheric nitrogen is not available to vegetation.
In discussing "The Economy of Nitrogen" from the standpoint of the then prevalent view, a writer in the Quarterly Journal of Science, some fifteen years. ago, said, "To economize nitrogen, phosphorus, and potash, to recover these bodies from waste, and to find substitutes for their present 'profligate' applications. is the most sacred task which the chemist can take in hand. The reforms which may shield us from occasional pestilence sink into insignificance compared with those required to guard posterity, in a not very remote future, from chronic scarcity, from recurrent famine, and from a wolfish struggle for food, in which man must relapse into a worse savagery than that from which he has emerged."
The evidence against the assimilation of atmospheric initrogen by plants came from experiments in which the conditions differed considerably from those of ordinary plant growth. In a series of experiments by the writer, the results of which were published in 1883, plants (peas) were grown in sand to which water with plant-food in solution was applied, but under conditions otherwise normal. They were found to contain, when ripe, much more nitrogen than was supplied in the nutritive solution and seed. The only possible source of this extra nitrogen was the air. A conclusion, so opposed to the commonly accepted be
lief, was received with hesitation, and very naturally So. But in the years following, a number of other experimenters obtained similar results. Several, among whom Professor Berthelot of Paris is chief, have found evidence that soils acquire nitrogen from the air to a much greater extent than was formerly supposed, and it is now probable that they get this nitrogen by the aid of micro-organisms. And what is still more to the point, Professor Hellriegel, of Germany, his, during the past ten years, made several hundred experiments and not only found that the leguminous plants, pea, lupine and serradella, which he has grown, acquire large amounts of the free nitrogen from the air, but has brought very strong proof that microbes are the agents by which it is done. These results have been most abundantly confirmed by those of a number of other investigators.
How many species of plants have this power of getting nitrogen for themselves from the air, and the details of their ways of doing it, are matters still to be found out. But it is certain that clover, and probable that the legumes in general, have this power. That this is all true is being admitted to day even by those who have formerly been the strongest upholders of the opposing doctrine.
The practical bearing of all this is evident. Nitrogen is the costliest of the elements of plant-food used in fertilizers. Farmers throughout the older portions of our country and in Europe pay from 10 to 25 cents per pound and more for it in guano, nitrate of soda, sulphate of ammonia, dried blood, meat scrap, and other commercial fertilizers. For these materials the farmers of the United States expend millions of dollars, and the supply of some of them is being gradually used up. By raising leguminous crops, which are in many ways the most valuable for fodder, this nitrogen can be had from the air without money and without price.
ENERGY AND FOOD-PRODUCTION.
The supply of plant food thus seems to be assured. But the population of the earth may become so dense.
that very general irrigation will be necessary. rivers, the lakes and the sea will furnish water, if it can only be transported. This requires power, energy. Will the energy be forthcoming? Is it at hand?
We are accustomed to think of burning wood ard coal as the chief sources of power. But their energy is nothing in comparison with that of moving wind, rivers and tide, and even that fades into insignificance in comparison with the energy of the sun's heat, a source of power so great that we can scarcely conceive of its vastness. When we reflect that, remarkable as are the uses we already make of the different forms of energy, our knowledge of them is still in its infancy, that we are apparently much nearer the storage and transport of the energy of stream and wind and sun than our grandfathers were to what we realize today in the use of steam and electricity, it takes no great faith to believe that science and invention will, in due time, supply the need. And with this use of mind to make the forces of nature do what has before been either done by the labor of our hands or left undone, the natural order of events will continue to bring what the progress of the past has brought, more product and larger profit with less manual toil.
Instead of the yield of a dozen bushels of wheat from the poor or exhausted soil of an acre, which was, a comparatively few years ago, a common average in England and is to-day in a large portion of the United States, thirty bushels of wheat per acre has come to be an average with better culture in England and will come with us when the demand calls for it. It is not to such increase as this, however, that we must look for the food supply of the future, but to such yields as come with sand and water culture. We are not restricted to the thirty or sixty or one hundred fold of the New Testament parable, but may look for the thousand-fold that is realized with abundant supply of plant food and water without any regard to soil.
Nor is there anything abnormal in such vegetable production. That a single plant should produce eight hundred seeds, as Professor Nobbe's buckwheat plant did, when fifty would be a large yield in ordinary practice; that the produce of a given area should
be scores or even hundreds of times what we ordinarily see; that half a dozen crops should be grown on the same area every year instead of one, is not what we are accustomed to, but is not at all unnatural. What we call luxuriant growth is really stunted growth. Our plants are subject to fluctuation of temperature; they have too much or too little moisture; their food-supply is scant or one-sided, and the very hindrances to their growth have had the further effect of preventing the development of varieties capable of producing the largest amount of the most valuable material. Let plants be trained by selection and cultivation to do their best; let them have the opportunity which comes with proper regulation of temperature and moisture and food; then perhaps we shall see what nature can and will do for us. As well say that the philanthropist is the abnormal, and the untutored child of nature the norinal man, as that there is anything abnormal in such large vegetable production.
ARTIFICIAL PRODUCTION OF FOOD. CHEMICAL SYNTHESIS.
But even if there were no such probability of almost unlimited vegetable production, there is still a possibility for food-supply in artificial manufacture by chemical process. Plants take the elements, carbon, oxygen, hydrogen and nitrogen, and combine them, in the forms of starch, sugar, oils, gluten and other compounds which serve to nourish animals and man. Within the memory of many che nists now living, it was believed to be impossible to build up such com pounds from their elements by artificial means. But chemistry has found means to imitate these processes of combination. Within the past few years many such compounds have been produced in the laboratory by synthesis. The advance of science in this direction is not enough to warrant any prophecy of the synthesis of food material--indeed, such a feat seems almost visionary-but it is hardly safe to say that it is impossible, and there are those who are confident that
it will be done.
Farming by water culture or the artificial manufac ture of food compounds would not be feasible or profitable to-day. The growing of a buckwheat plant