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TAE Marine REVIEW ! '4l distortion corroborated the correctness of the theoretical con- clusions. Rotating discs therefore, really do "burst" when they go to pieces, that is, they explode in such a manner. that they are rent to pieces by forces which tear the fibre of the material, first on the inside, the rents rapidly being transmitted to the outside. This investigation is of considerable «interest with regard to the bursting of emery wheels and grind- stones, and it throws much light upon the proper and eco- nomical design of wheels of any kind, rotating at high speeds. With the aid of the data obtained through these theoretical 'and experimental investigations, the foundation of design of the rotating elements of these large machines has become well secured, and the determination of the maximum internal stresses in the nickel steel plates composing the rotating 'field, illustrated in Fig. 3, can be made with considerable con- fidence. The structure of the rotating field consists: of ten nickel- steel forgings pressed on a_ nickel-steel 'shaft. In order to obtain both high magnetic permeability and good mechani- cal strength, nickel-steel, containing approximately from 3 to 5 per cent nickel, has been used whose lowest elastic limit is 50,000 Ib. per square inch and whose lowest ultimate strength is 80,000 Ib. per square inch. The highest stress existing in any one part of. the rotating element does not exceed 15,000 lb. per square inch.. At-normal speed, there- fore, the lowest: safety factor is almost 514, showing that these rotating fields might be run at twice their normal speed without flying asunder. -A problem of extreme. difficulty eonteodig the designer in tee. and securely fastening the field windings to these large steel blocks in such a manner that neither the copper conductors nor the insulation between them and the magnetic field can be injured: by the centrifugal force to which thev are exposed. 'To this end flat copper strips have been wound on 'special designed formers, which are made in 'such a: man- ner as to give an ever- increasing opening to each sucessive 'turn, and they are lodged in radical slots, milled into the nickel-steel discs, and held in place by retaining : wedges made from Parsons: manganese bronze. The construction is so solid that it might well be said that a cannon could not be made stronger and more reliable. The end connections of the field coils rest against nickel-steel end rings, which also are shown in Fig. 3. Owing to the rotation of the revolving field, air is blown through the ventilating segments of the stator, cooling the core as well as the coils. The efficiency of this ventilation is well demonstrated by the fact that, though operating at a core loss of 47 per cent above the normal, the temperature rise of the core, after continuous operation, did not exceed 22% degrees C., and this result was obtained with compara- tive little noise and power. The satisfactory ventilation of the field coils has also been demonstrated. The electrical efficiency of this generator, as actually ob- tained from tests, is 94.4 per cent at 4 load; 97 per cent at 14 load; 97.9 per cent at 34 load; 98.3 per cent at full load; 98.5 per cent at 114 load, and 986 per cent at 1% load. The regulation of the generator at full load at 100 per cent power factor is 7% per cent, and yet the generator has enough margin to give its full rated output on any power factor, however low. Another question of great importance in 'he design and operation of the high-speed revolving-field generators! is created by the tendency towards vibration which, in improper- ly designed machines, may become a source of very serious difficulty. The heavy mass of the rotor, put on a shaft, cor- responds exactly to the mathematical combination of a mass and a spring attached thereto, which is the simplest form of a vibratory system. Such a system, by alternately yielding up and storing energy, is capable of vibrating violently under miles an hour. certain conditions favorable to the existence of such vibra- tions, and it becomes a problem of paramount importance to determine the natural period of vibration of the rotating element of a generator operating at such high speeds as the. large machine here described. By carefully studying this problem and choosing stch dimensions for the shaft of the machine as will correspond to the natural vibration of the rotating element, as much different as possible from the period of vibration produced by unbalancing at the normal rotative speed, it is. possible to obtain safe and steady operation without fear of vibration! To steer clear among the many reefs that beset the course of the engineer in the creating of large apparatus designed upon lines heretofor unknown is a problem all the moré interesting because of its difficulty. STRANDING OF THE CHEROKEE. The Clyde Line steamer Cherokee ran ashore in a fog on Brigantine shoal off Atlantic City and was exposed to the full force of the Atlantic: The rescue of her passengers and STEAMER CHEROKEE STRANDED, crew is one of the most daring and most brilliant acts in the annals of the sea. _ Thousands of dollars were later subscribed by the rescued and given to the rescuers. The cargo was thrown overboard in the hope that the vessel thes lightered would 'rise 'but so far she has not done so. NEW. STEAMER FOR THE ST. 'LAWRENCE. The Richelieu & Ontario. Navigation Cor Montreal, has let contract for a twin-screw passenger steamer for the St. Lawrence River Rapids Line. The new steamer will be 240 'ft. over all, 41 ft. beam at main deck, 43 ft. beam over wales and 6 ft. draught. She will have ninety-four staterooms, four parlors and two bath rooms. Her speed will be 18 The promenade deck will have for- ward a large observation space for passengers. Next after this will be a' cabin for sheltering passen- gers in stormy weather.. The space after this cabin to the stern of the boat will be devoted almost entirely to stateroom accommodations' for' passengers, with merely a small cabin 'at the after end of this deck just forward of a small open passenger .space at the extreme stern. The hur- ricane deck -will be left entirely open, that is, with no ob- 'structions whatever except fot. a small cabin: with staterooms and will be used as an observation. room for passengers when running the rapids. The hurricane deck will be extended to the stern of the: boat and will be covered with a light: awning roof. The pilot house and texas will be on this deck, the pilot house being. sufficiently 'raised: for handling the boat -with passengers in front of the pilot house. The steamer is expected to go into service 'during the coming season. She 'will 'be built by the Canadian Ship Building Co., Toronto. The company is now making arrangements for a full-sized canal passenger and freight steamer for the Hamilton- Montreal Line and also for. a steamer for the Montreal- Quebec route to run opposite of the steamer Montreal, which is one of the finest passenger boats in Canada,