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have to be adopted to keep the producer hot enough on these occasions. Having now generally, described the producer, the difficulties and advantages of adapting the gas engine itself to ma- rine work will be considered. The one great disadvantage of the in- ternal combustion engine is the necessity of setting the engine in motion before it will. run automatically. For powers less than 200 horsepower, it is preferable to employ a reversing gear, keeping the engine always running in the same direc- tion, or to use a reversing propeller. Compressed air is. being employed. 'for starting up large engines, and when once the engine is fitted in this way, the valve gear for running the engine in either 'di- rection does not amount to very much. For moderate powers, a single acting engine with a trunk piston is found most convenient, as the piston does not require to be water-cooled, until one as much as about 2 ft. in diameter is etnployed. <A single cylinder of 20 in, diameter and 2 ft. stroke, running at 120 revolutions per" minute, will give about 100. horsepower, _ taking the average working pressure at about 80, which is less than the figure often obtained. The same sized cylinder, Mosking as a. ' double-acting cylinder, would, of course, double the horsepower; but, besides the additional valves, which must be an exact duplicate: of those required for a single- acting engine, there is the complication of the watef-cooled piston and rod. This at first sight will appear somewhat serious to the marine engineer, but when the very large number of engines of this design which are working on land are considered--the regularity with which they are run; and the little attention they require--it will be agreed that there does not seem any reason why they should not meet with success at sea. For. small plants of from 100 to 200 horsepower, a small auxiliary internal combustion motor, driven by oil or some other fuel, is found.most convenient for blowing up the producer, for starting it, and also for starting the main engine. For larger powers fitted to vessels where steam capstans and steering gear are fitted, it is thought that the best plan will be to employ an auxiliary boiler, which.can be heated by the gas when the whole plant is at work, and can be used independently to drive the various auxil- iary and starting engines when the pro- ducer is not alight. ! The average heat efficiency of steam boilers is taken at about 66 per cent, _ Professor Capper has stated that the theoretical maximum thermal efficiency of the steam engine is only 30 per cent, and only from's5 per cent to 20 per cent ' of the heat generated is, ever turned into uséful' work. In 'the case of the .gas engine, the theoretical efficiency is about TAE Marine REVIEW 80 per cent, and in practice 25 per cent to 30 per cent of heat developed in the cylinder is turned into useful work. For vessels fitted with small-powered compound-condensing engines of less than 100 horsepower, the fuel consump- tion willbe from 2 to 3 Ibs. pet. 1.H.P. For gas plants of this powér the fuel consumption will be less than 1 Ib. per I.H.P. For larger powers of not less than 500 horsepower the economy will not be quite so marked, but will be about as, follows: Steam plant, say; 1.6: 1b, per I. H. P. (cas plant, say, 0.6 lb, per J. H.-P: At this figure of one-half, plant should be well worthy of adoption from an economical point of view, as, in other words, the same coal will do double the work. The stoking and the cleaning of the fire of the producer are much less than would be required for a steam boiler of the same power, the stoking being prac- tically automatic, and practically the whole fuel other than the clinkers is consumed. From the plants made, and from de- signs that have. been got out for mod- erate powers, it would appear that the space occupied by the gas generator and engine is about the same as the steam plant; but for large powers, where a double-acting gas engine is employed, the weight will be considerably less, as the engine will be about the same weight as the steam engine, and the producer will be very much lighter than the boiler. The type of engine adopted by Herr Capitaine for his small powers is built with a plate frame, no casting being em- the gas ° - ployed in the engine other than the. cylinder itself. A light ehgine is thus obtained, and there is no danger of breakage resulting from the very high pressures employed. Figs. 5 and 6 show the engine fitted to the vessel which ran in the reliability trials in the Solent last summer, which was named Emil Capitaine, after the inventor of the system, The official report of the trials shows that this boat of 16-tons displacement ran at an average speed of 10 miles per hour for 10 hours, on a consumption of 412 Ibs: of anthracite coal: This consump- tion also includes the fuel which was consumed by the producer during the previous 12 hours, when it was not in active operation, but simply smoldering and keeping itself alight, the producer having been filled the night before the trial. The amount of fuel consumed in this way is very little, but should be taken into account when making a consumption trial. Several tugs, boats and other: vessels have been fitted with similar engines to the one illustrated, and are at the present and producers. time running on. the Cgntinent on the. inland waterways; but, as far as ,is known, the Emil Capitaine was the first vessel fitted with a gas engine and pro- ducer to run in the open sea. : For the purpose of comparison, tests were made on November 8, 1904, with the Gastug No. 1 and Elfriede, a steam tug of very-nearly the same dimensions and power. The Gastug No. 1 is 44 ft. 3 in. long by 1o ft. 6 in. beam, and is fitted with one of the 4-cylinder - 70 horsepower suction gas plants. The El- friede' is 47 ft. long by 12 ft. beam, and is fitted with a triple-expansion steam engine developing 75 horsepower. At the towing meter the Gastug No. I at- tained a maximum pull of 2,140 lbs., and the Elfriede a maximum of 2,020 lbs. A run from Hamburg to Kiel and back was made by these two boats, during very stormy weather, at a maititained speed of 8% knots.. The consumption of fuel was 'measured for a period of 10 hours, and was as follows: For the Gastug No. 1, 530 Ibs. German anthracite; for the El- friede, 1,820 Ibs. steam coal. This shows: an economy of I to 3.44 in favor of the gas plant. Messrs. the well-known Deutz, gas -engine builders of Cologne, have fitted - one of the large Rhine barges with two of their two-cylinder land type engines 'The vessel is of 200 tons carrying capacity, and is said to have given satisfactory results, running on the Rhine between Rotterdam and Co- logne. CANAL BARGE, : To determine the suitability of the Capitaine system for small powers, a canal barge (Fig. 7) has been fitted with a two-cylinder 35 horsepower engine, and it has been sent on an. extended trip over the English canals. .She left Brent- ford in charge of Mr. B. Dunell on Jan- uary 3, fully loaded herself, and towing two ordinary canal barges, which she took to Birmingham. After various demonstrations there, ceeded to Manchester, giving she pro- and. after mak- ing further trials there, worked her way back to the Thames at Oxford, returning to Chiswick at the end of February. The total fuel consumed on the round trip, and the various demonstration runs she made at the different places, was 5 tots I cwt., the engine having been under way for 40 days. . The only difficulties experienced on the trip were due to the shallowness and the bad state of many of: the canals; the water inlets on several occasions becom- ing choked with mud, and the pro- peller, which was. of the reversing pat- tern, damaged by coming into with different sorts of rubbish, which had been allowed to accumulate in the canal bed. It would appear that the only sort of propeller suitable for canal work contact