LIQUID FUEL
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.
As used at present liquid fuel simply substitutes coal for heating the ordinary type of boiler. But there seems every reason to believe that in the near future some type of internal combustion engine will be perfected that will use the crude, cheap oil, as the finer and lighter oils are used in motors to-day. When this occurs the space-consuming boilers and furnaces used in ships at present will be replaced by compact machinery, quite as efficient, but occupying only a fraction of the space. Nor need we expect that the invention of some such type of engine will be long delayed, if we may judge by the rapid strides made in perfecting other internal combustion engines during the past few years.
III
SUBMARINE VESSELS
THE development of submarine vessels has been one of the slowest in the history of modern inventions. Submarine boats, using submarine torpedoes, were able to destroy ships a hundred years ago; and a little less than half a century ago naval vessels were destroyed in actual warfare by these boats. But curiously enough no vessel has ever been destroyed in actual warfare by a submarine boat since that time. Yet these boats are essentially war-vessels, and, with the exception of boats of the Lake type, of no use whatever for commercial purposes.
Perhaps the explanation for this tardy development lies in the fact that until recent years naval men have not looked with favor upon this style of fighting craft. In Admiral Porter's book, written in 1878, he makes the statement that one of the reasons why they did not show more enthusiasm about the submarine made by Robert Fulton early in the nineteenth century, was that such boats "menaced the position of the naval men, whose calling would be gone did the little submarine boat supplant the battle-ship." We need not, however, depend upon this statement, made as it was three-quarters of a century after the demonstrations by Fulton, for there are many similar statements made at the time to be had at first hand. Thus Admiral Earl St. Vincent, when opposing the views of William Pitt, who had become enthusiastic over the possibilities of Fulton's submarines, is on record as having opposed such craft on the ground that by encouraging such development "he was laying the foundation which would do away with the navy." In 1802, M. St. Aubin wrote in this connection, "What will become of the navies, and where will sailors be found to man ships of war, when it is a physical certainty that they may at any time be blown into the air by diving boats, against which no human foresight can guard them?"
Such opposition has undoubtedly tended to retard the progress of submarine navigation; but be the cause what it may, it has made slow and laborious work of it; and we are only now approaching a solution of the question that seemed almost within grasp a hundred years ago—before the days of steam or electricity.