-THE REVOLUTION IN FUEL.
As nearly always happens, a technical invention was fated to alter the relations between nations and to threaten the stability of empires.
For half a century, oil was simply a means of lighting ; its use was confined to the lamp, and occasionally the domestic stove. Moreover, in this modest sphere, it had to meet the competition of gas and electricity ; and at one time there was some thought of restricting its pro duction. Between 1900 and 1910, the perfecting of the internal combustion engine and the enormous develop ment of motoring gave it a new lease of life ; prospectors spread over the fields of Mexico, Central America, and Burma, and production increased still more quickly than the demand.
Now, all these new engines consumed petrol alone. Under pressure of the demand, it became customary to raise and refine poorer and poorer oils, giving from 6o to 75 per cent. of wastage ; only a part of this residue was used in the form of lubricating oils. There remained the mazut or fuel oil, which, it is true, could be burned, but had a high flash-point and deposited carbon too quickly for use in the delicate engines of motor-cars, lorries, and aeroplanes.
Such was the situation when a German named Diesel constructed the first internal combustion engine for heavy oil. The mazut, subjected to great pressure in the cylinder, produced an explosive mixture, which, without sparking-plug or magneto, drove the pistons in the manner of the petrol engine. The starting of the Diesel engine required a powerful machine to obtain the necessary pres sure, which rendered it unsuitable for vehicular transport, but it could be used wherever a sufficiently heavy installa tion was permissible ; and burning as it did an almost worthless by-product, the net cost of running it was low. Finally, since with this machine there is no longer any need for boilers, and also mazut, compared with coal, gives the same number of calories in a smaller volume, a Diesel engine takes up much less room than a steam engine of the same power.
A revolution followed. Wherever no great or rapid variations in power were required, Diesel engines began to be employed. Shipping especially made use of them ;
applied originally to fishing-boats and coasting vessels, they gradually increased in use for long voyages. A vessel fitted with a Diesel engine can sail for fifty-seven days without rebunkering, while with a steam engine it could not sail for more than a fortnight. Oil, confined at first to industries on land, began to conquer the seas.
Nevertheless, in spite of numerous improvements, the internal combustion engine enjoyed so far only a com paratively modest success, and the great liners seemed beyond its range. Then came the idea of introducing the mazut directly into the furnaces of great ships. Since it great quantities of oxygen in burning, powerful injectors were contrived for fitting to the furnaces in order to convert it into spray, mingle it with air, and so facilitate combustion. By means of these supplementary inexpen sive installations and small alterations in detail, ships of any size can now be converted to burn oil in a short time and at small cost.
The advantages of such conversion are enormous. For the same weight fuel oil gives 7o per cent, more heat than coal. It is less bulky ; it is not dearer ; it is easily manipu lated, for it flows by itself into the machine ; it economises labour considerably ; it permits of more rapid variations in speed. Giving out more heat for a smaller volume, it increases the radius of action about 5o per cent. with the expenditure of the same power, and also allows of a saving of 3o per cent. in bunker space. This last-mentioned fact is specially important for armoured vessels, which can in consequence be armed with more powerful guns. Hence the British super-dreadnoughts, like the Queen Elizabeth, burn only oil, as do also the great American battleships Nevada and Oklahoma. The naval authorities of the United States have completely given up the use of coal in the new capital ships under construction. The great shipping companies have likewise fitted their recent liners to burn liquid fuel. In naval and in merchant shipping, mazut is on the way to dethrone coal.