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the Otto cycle (four-stroke type). Gen- erally speaking, all these systems have given equally satisfactory results, and it is, therefore, difficult to say which offers the greatest advantages. As the marine gas engine is only following the lead taken in land gas engines, it will not be out of place to offer a few remarks concerning the latter. Ten or twelve years ago en- gines of 500 to 600 H. P. were built "THE MarRINE REVIEW der. The mixture chamber with the inlet of gas and air is in the center. Large jacketing is shown all round the cylinder, including- the stuffing box packing, as is also shown the piston jacketing with inlet along the piston rod and outlet through the tail-rod. As the exhaust valves underneath the cylinder take up considerable space, the cylinder is supported at the ends only. A single glance at the design ELEVATION 53 three sets of 100 B. H. P. kerosene motors, having four cylinders each of 8 in, diameter and 8 in. stroke, making 750 revolutions per minute. Lubrica- tion is forced to all bearings. The starting is effected by compressed air, supplied by a 6 B. H. P. motor and compressor, and reversing is accom- plished by means of clutches, which make the whole plant as easily con- trolled as a steam engine. Reduced See SS SS ees on ee ee el i PLAN FIG. 7---GENERAL ARRANGEMENT OF MACHINERY IN THE TRIPLE-SCREW YACHT BRONZEWING. on the Continent for the purpose of utilizing the waste gases of blast fur. _ naces, and were called "poor gas en- gines". The types manufactured 'by the Deutz, Augsburg, Cockerill, Kort- ing and Oechelhauser companies may be considered the most wp-to-date, and there exist quite a number of these en- gines of from 1,000 to 1,200 H. P., and even higher powers. In the United States, engines up to 4,000 and 5,000 H. P. have been built. Figs. 5 and 6 are sections of a Korting double-act- ing gas engine, which is one of the horizontal non-reversible type, with inlet valves on top and exhaust valves at the bottom of each end of the cylin- shows its complicated nature, which is bound to further increase if applied to vertical engines and if a reversing gear be added. It is. not surprising, there- fore, that progress with the marine gas engine has been slow. In regard to oil engines, we will only consider the Thornycroft and Diesel motors. The former has been fitted in a great many small craft, and may 'be considered as one of the best types of marine motors built in this country. Figs. 7 and 8 represent a set of engines just fitted by Messrs. Thornycroft in the triple-screw yacht Bronzewing, 120 ft. long by 17 ft. 6 in. beam. The machinery consists of speed is obtained by leaving out either the center or both wing motors. The Diesel motor, which has 'been specially developed on the Continent, and up to the present appears perhaps the best adapted for marine purposes on a large scale, is a single-acting, four-stroke, non-reversible marine en- gine, and therefore leaves room for improvement in regard to reversibility. In the first applications the difficulty was overcome by driving the shafts with electric motors. The next step was to drive the shafts directly from the main engines for ahead motion. Then going astern an electric motor is thrown into action, requiring only