from the soil except nitrogen, only increased the crop to 15 bushels per acre. Manuring with nitrogen on the other hand increased the crop to 21 bushels per acre. Obviously on the Rothamsted soil wheat has great difficulty in getting all the nitrogen it wants, but is well able to fend for itself as regards what Liebig called minerals. This kind of experiment has been repeated on almost every kind of soil in the United Kingdom, and it is found that the inability of wheat to supply itself with nitrogen applies to all soils, except the black soils of the Fens which contain about ten times more nitrogen than the ordinary arable soils of the country. It is the richness in nitrogen of the virgin soils of the Western States and Canada, and of the black soils of Russia, that forms one of the chief factors in their success as wheat-growing lands. It must be added, however, that continuous cropping without manure must in time exhaust the stores of nitrogen in even the richest soil, and when this time comes the farmers in these at present favoured regions will undoubtedly find wheat-growing more costly by whatever sum per acre they may find it necessary to expend in nitrogenous manure. The world’s demand for nitrogenous manure is therefore certain to increase. Such considerations as these inspired Sir William Crookes’ Presidential address to the British Association in 1898, in which he foretold the probability of a nitrogen famine, and explained how it must lead to a shortage in the world’s wheat supply. The remedy he suggested was the utilization of water-power to provide the energy for generating electricity, by means of which the free nitrogen of the air should be brought into combination in such forms that it could be used for manure. It is interesting to note that these suggestions have been put into practice. In Norway, in Germany, and in America waterfalls have been made to drive dynamos, and the electricity thus generated has been used to make two new nitrogenous manures, calcium nitrate and calcium cyanamide, which are now coming on to the market at prices which will compete with sulphate of ammonia from the gas works, nitrate of soda from Chili, Peruvian guano, and the various plant and animal refuse materials which have up to the present supplied the farmer with his nitrogenous manures. This is welcome news to the wheat grower, for the price of manurial nitrogen has steadily risen during the last decade.