its activities could hardly have been expected. We refer to the manufacture of hydrogen and oxygen. Strange to say, these two gases which had never found any industrial application, although known since the birth of chemistry, have lately become of the greatest technical importance and are to-day manufactured on a tremendous scale. Hydrogen is used for military purposes in immense quantities for all lighter-than-air flying machines—the filling of Zeppelin ballonettes, the filling of captive balloons, which have become of such great importance in modern warfare, being constantly employed by the staffs of the armies for observation of the battlefield. By telephone and photography they are in constant communication with headquarters.
The cheap and practical methods which were evolved by the military authorities for the generation of hydrogen are now utilized in one of the industries which has recently become of the highest importance, namely, the manufacture of what is called "hardened oils and fats." By treatment with hydrogen, oils and fats in the liquid state are converted into solid materials, which usually command a higher price for technical purposes, such as the manufacture of soap, etc.; and low class fatty substances, which are not fit to be eaten on account of their appearance or odor may be transformed into valuable food materials. By the economical manufacture of hydrogen, which makes it possible to utilize such inferior goods for alimentation, German militarism again deserves well of the nation. It must also be noted that the cheap production of hydrogen is one of the prominent features in the above mentioned manufacture of sulphate of ammonium according to the Haber process. Thus the manufacture of hydrogen, while originated for military purposes, is helping to feed the nation by providing new edible substances, on the one hand, and a new source for fertilizers, on the other.
The manufacture of oxygen likewise assumed gigantic proportions, after it was found that armor plates could be cut almost like butter by the heat of the flame from a burner fed with a mixture of hydrogen and oxygen, or oxygen and acetylene gas. At present, not only the cutting but also the welding of iron and steel is accomplished by means of such a flame; every machine shop is provided with an oxygen apparatus, and soon every garage will be similarly equipped, as it has been observed that the carbon collected in the cylinders of gas engines for automobiles, etc., can be easily removed by burning it out with the oxygen-flame.
The oxygen problem also plays an important part in the running of submarine boats where it is necessary to provide the crew with oxygen for breathing under particularly difficult circumstances. It is stated that nitrogentetroxide, a gas which can be easily compressed to a liquid, and which, when appropriately heated, decomposes with the liberation of oxygen, has been employed for this purpose with great success. But for the necessity of supplying oxygen to the submarine boats, this sub-
