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fapid and noiseless handling of baggage and stores; and on_ this ship another novel contrivance will be an electric ele- -yator running from the salon (or up- per) deck to the upper promenade deck. A Marconi house with apparatus will be fitted on the upper promenade deck aft, and in addition the ship will be fitted with a submarine signaling apparatus which allows communication through the water at a distance of several miles, whereby in fog the ship can be signaled from lighthouses or dangerous points on the coast, this constituting another im- portant element in the safety of the ship. BALANCING PROBLEMS. "The Effect and Importance of Balanc- ing in Internal Combustion Motors Ap- plied to Marine Propulsion" was the title of a paper read by Mr. A. T. Weston, M. 7 Sc, Stud, Inst' C. E., recently before the students of the Institution of Civil Engineers. Mr. Weston said that much progress had been made in recent years in the development of high-speed steam engines, more especially in the type of engine adapted to the propulsion of fast vessels, such as torpedo boats and de-. stroyers. His concern was chiefly the usual type of high-speed petrol motor, but the same principles applied to all classes of engines, irrespective of the nature of the combustible element. The application of the petrol motor to marine propulsion opened up a field of develop- ment, which, from the point of view of production of power, was unlimited; hence the demand for a motor capable of developing considerable power, and com- bining all the advantages of motors suitable for automobiles, became univer- sal as soon as the possibilities of the case were fully recognized. The suc- cess of. the internal-combustion engine as a marine motor depending largely on its fundamental property of producing a large factor of power per ton of ma- chinery, it was desirable that this prop- erty be retained in engines of large power; and as the horsepower developed is proportional to speed caeteris paribus, this would involve the prodiuction of power at a high speed of revolution. While no great difficulty was experienced in running a small multi-cylinder engine in which the reciprocating parts were cut down in weight as much as possible con- sistent with strength, directly the larger efigines were introduced the rapid recip- rocation of the heavier masses gave rise to serious difficulties owing to the vi- bration set up. In the earlier type of racing vessels in which the peculiar properties of the pe- trol motor were utilized to their fullest extent, the effect of the vibration was most deleterious on the structure of the hull, and seriously affected the reliability of the engine itself. The cause of the -inders, in the central plane. _ TAe Marine REVIEW vibration and many similar troubles was not a little obscure. As was well known, to effect a-complete absence of vibration in any revolving system, it was essential that all the reciprocating and revolving masses should be in balance as regards inertia forces. But it was at once evi- dent that the usual arrangement of four- cylinder motor engine with cranks at 180 degrees was a system in which the balancing of primary forces and couples was complete. Hence the cause of the vibration appeared more deeply involved than one might. have surmised. Mr. Weston then dealt with the mathemati- cal equations for balancing, which were given fully by Herr Schlick in his pa- per before the Institution of Naval Ar- chitects in 1900, and which could be ob- tained also from Professor Dalby's book. on "Balancing." Continuing, Mr. Wes- ton said it might appear that with an en- gine designed for a low speed of revo- lution, but at the same time retaining a high piston speed, a good result would be obtained for it; it would be run at a speed so slow that the secondary unbal- anced forces might be of no consequence. But there was a well-defined limit to the degree of compression, beyond which it was impossible to go, without incurring the dangers of premature ignition, and therefore a limit to the length of stroke possible, unless the clearance volume was also increased proportionately. Length- ening the stroke also involved a corre- sponding increase in the length of the cylinder and water jacket, and either of these expedients would require an in- crease in weight, which was fundament- ally objectionable. From these considerations it would ap- pear that the balanced type of four cyl- inder engine had every advantage, where a high speed motor using a heavy coil was desirable, such as obtained, for ex- ample, in submarine and_ torpedo-boat work. The arrangement for a six-cylin- der engine was equivalent to an imag- inary system of three engines with cyl- inders coincident in the central plane, but with the respective cranks arranged at 120 degrees apart, which system was known to completely satisfy the condi- tions for complete balancing. The five- cylinder balanced engine was similar to a six-cylinder engine with its two center cylinders and cranks merged into one large cylinder, of double the weight of the reciprocating parts of the other cyl- A five-cyl- inder engine arranged in thi. way would not give such an even torque as the six- cylinder engine, but in all other re- spects it would be quite as good. From a knowledge of up-to-date practice it would seem that where space could be allotted for it, and prime cost was of secondary importance, high speed engines of several hundred horsepower capacity would be made of six cylinders. The smoothness of running and complete ab- sence of vibration in such cases as al- ready existed were amongst their most prominent features. A FIREPROOF FERRYBOAT. A fireproof ferryboat just completed for the Pennsylvania railroad ferry be- tween Philadelphia and Camden is note- worthy for the use above the main decks of steel plates and structural shapes in place of wooden stan¢hions, carlines and sheathing. The outside framing consists of double channel window posts with horizontal angle bracing, and the inboard cabin bulkhead is made of heavy. angle and I-beam posts, to which -is riveted 8-lb. plate sheathing. Each window post consists of two 4-in. CrRoSS SECTION OF STILE channels with 5-lb. plate covers, to which the window frames are fast- ened directly. The ornamental inte- tior finish of the cabins consists of panels of asbestos building lumber, which are screwed to small wooden blocks bolted to the inboard bulkhead posts, and finished with drawn-steel mouldings. The seats in the cabin are made of drawn- steel mouldings supported on steel angle- bars. The window sash, window sills and frames are of wood completely cov- ered with sheet copper of No. 18 gage. The pieces of wood forming these parts are first moulded in the section desired, then loosely wrapped with copper, and both together are drawn through dies that press the copper firmly down on the wood and lap-joint the edges of the copper sheet. The new twin-screw steamer now building at the yard of Harland & Wolff, Belfast, for the Holland-American line, will be named Rotterdam. The vessel is of 23,700 tons register. The Rotterdam will probably be launched late this year and will make her maiden voyage to New York in April, 1908.