Another step that has been taken to increase the efficiency of the steam engine on ships, is the adoption of liquid fuel in place of coal for making steam. For years the advantages of this form of fuel have been recognized, the Russians having brought its use to a high state of perfection, both in boats and locomotives. Practically all the steamers on the Black and Caspian seas, as well as on such rivers as the Volga, burn oil exclusively. And early in 1910 the British Navy decided to substitute oil for coal on all its vessels. The advantages claimed for oil over coal as fuel are many. It is smokeless, produces more heat than coal, occupies less space for storage, can be loaded more quickly and easily, is cleaner, and reduces the engine-room force to one-fourth or one-third the number of men required when coal is used. Incidentally it reduces the difficult physical task of stoking to one relatively pleasant and easy. It gives a steadier fire, does not foul the boilers, and does away with cumbersome ashes and clinkers. Its disadvantage lies in the danger from fire. An inflammable liquid carried in a ship's hold is obviously more dangerous than a corresponding quantity of relatively incombustible coal. Yet the obvious advantages of this form of fuel have been so compelling that it is now coming into use on all classes of war vessels, and seems likely to supplant coal entirely on some types of boats, such as the torpedo destroyers. Moreover, the experience of the Russian boats on the Black and Caspian seas seems to indicate that the dangers from the use of oil as a fuel when properly handled have been greatly exaggerated, and passenger and freight steamers all over the world are gradually adopting it. Some tests were made by the Navy Department of the United States in 1909-1910 using a vessel which was formerly a coal-burning boat. In these tests it was found that the steaming radius was greatly increased, the firing force reduced, and fuel taken into the ship in about one-fourth the time it takes to coal. It was possible to get up steam in any boiler, or set of boilers, much more quickly than with coal. Of course where oil is used for fuel some special form of burner is necessary. Many types have been tried, but in the most effective the oil is atomized by the use of steam spray, or air blast, it being impossible to get proper combustion of the oil except when used in minutely divided particles. Used in this manner a uniform temperature can be maintained easily, or may be increased or decreased very quickly.