Mr. Brooks is speaking exclusively of the part that petroleum plays in the industrial and social life of Great Britain. In the United States its applications are wider still. Were it necessary, it would be possible to dilate on the relation of petroleum to agriculture in this country, where the farmer who operates a large acreage in the middle west or in Texas and California, by means of tractors finds petroleum an indispensable ally. In this sense petroleum has helped enormously to increase the food supplies of the world and the national wealth of the United States. One of the greatest, if not the greatest of modern industries on this continent--the manufacture of motor cars--would to all intents and purposes be non-existent were it not for one offspring of petroleum (once regarded as almost the least valuable product of the refinery) gasoline. Invention has reacted radically on the oil industry, from decade to decade, and especially on its refining phase. Until the advent of what is known as the “internal combustion” engine, for instance, the demand for gasoline was so limited that when produced, as was inevitable in the distillation of many types of crude, it represented but a fraction of its present value. To-day this engine, which lives and functions by gasoline, has created an ever-increasing demand for that fluid which taxes the energy of all refineries to meet. The internal combustion engine with the assistance of petroleum has indeed exercised such a powerful influence in changing the face of civilization as to demand fuller reference. It not only made the automobile practicable, but the aeroplane, the dirigible air-ship, the submarine and a host of other craft possible. When, during the autumn of 1919, the entire railroad system of Great Britain was paralyzed by a general strike, and the people of its great and overcrowded cities were face to face with starvation, it was admittedly the internal combustion engine, operated by gasoline (commonly known overseas as motor spirit or petrol)--that saved the situation. To understand its appellation the reader should note the fact that the older forms of engines were operated by steam generated in boilers, heated by external combustion--a process familiar to everyone. The internal combustion engine, on the contrary, runs by fuel (usually gasoline) which is introduced directly into the contrivance itself. There it is vaporized and mixed with air so as to become an explosive substance with great powers of propulsion. It is not difficult to grasp the immense saving of weight and space which is involved by the elimination of the boiler from the mechanism of an engine. During the war especially, the minds of all mechanical experts were applied to improvements that would result in an engine being made lighter and lighter with each new model, while at the same time meeting enormous power demands. Without such space-saving contrivances the flying machine would never have reached