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320 ALEXANDER MURRAY, THE CONSULTING _ ENCINEER. this the coal shogt had to be consid- erably lengthened and brought further over the steamer's deck. Upon ex- amination it was found that this coal shoot was, during the discharge of the fourth wagon, résting upon the steamer. As soon as the weight of the coal shoot was removed, the por- hydrometer correctly swung 'back and registered 40 tons, as the total amount taken on board from the four wagons. Here, undoubtedly, was a good ex- ample of the sensitiveness and ac- curacy of the invention, and those on board the Procida were very much struck by the fact that so small a quantity of cargo was, on a 7,000-ton steamer, so accurately recorded. The general opinion seemed to 'be that on barges and cargo s'eamers carrying deadweight material there was a fine opening for the invention, whilst it THE MARINE REVIEW would also be a useful addition to vessels of any class or description. It is pointed out that one of the many useful purposes to which the porhy- drome'er could be put is in deciding promptly and reliably whether or not a passenger steamer's ballast tanks are full, Yet another use would be in discovering a leak, ahd estimating the rate at which the water was entering the ship. Knowing this, it would be an easy matter to arrive at a decision as to the chances of the vessel being able to make port. Fitted on the mechanism is a bell, which rings if the ship springs a leak. Shipowners, of course, are anxious to know what saving they may exppect by the adoption of this invention. Vessels fitted with the porhydrometer have to pay to the Italian govern- ment a tax of 15f. per annum. Hav- ing paid this fee they may demand that the instrument be recognized by the custom house people, and instead of having to pay 23% centimes per "ton for the weighing of the cargo on discharge they get off with the small charge of 8 centimes per ton if the ship is equipped with the apparatus. There is, of course, also a very big saving in the time of discharge. Take the port of Genoa, for instance, where, under present conditions, only 500 tons per day can be discharged with- out having to pay the extra hours of labor. With a porhydrometer as much as 2,000 tons can be got over the side in a day, and this is permitted if the work is done in the recognized hours of labor. Roughly speaking, it is es- timated that the economy of time is about 75 per cent. All things consid- ered, it is not surprising that the in- ventor is optimistic as to the future of his invention. Duluth and San Francisco Fire Boats* By JoHN ODERN developments in the water-borne commerce of both inland and _ seaboard cities, with the consequent increased investment in ships, wharfage, ware- houses and other property on the wa- ter front, make the problem of im- proving the present fire-fighting facili- ties one of great economic importance. The extensive use of combustible ma- terials which still characterizes Amer- ican building construction, makes the relative effectiveness of different types of fire boats important factors in de- *Reprinted from the General Electric Review. Liston. termining insurance rates. Where fa- cilities exist for connecting the high pressure pumps of the fire boats to city mains, their sphere .of usefulness is not limited to the immediate vicinity of the water front, and they have been 'found in many instances to be valuable auxiliaries to the land fire fighting ap- paratus. While the general tendency in fire boat construction has been in the di- rection of larger boats and higher wa- } 'ibe "i Me ter pressures, local conditions must al- ways affect their design in regard to speed, capacity and ice-breaking and maneuvering characteristics. October, 1909 The practical value of a fire boat is largely dependent on the volume and pressure of the water which can be delivered by its pumping outfit. Here- tofore the usual equipment has con- 'sisted of double-cylinder, vertical, invert- ed reciprocating pumps, each unit havy- ing a capacity of about 3,000 gals. per minute; but the high steam pressures now demanded in fire boat service can be most economically and safely ob- tained by the use of centrifugal pumps driven by steam turbines. This com- bination, when compared with the re- ciprocating pump equipments ordinarily used in fire boats, has the following advantages: It shows a marked improvement in steam economy for a given amount of water delivered at the nozzles, togeth- er with a practical elimination of the strain on the -hull due to vibration which is inseparable from the use of reciprocating pumps. The absence of valve and other moy- ing parts required in the reciprocat- ing pump minimizes the cost of attend- ance and the replacement of worn parts. The two-stage turbine-driven centrifu- gal pumps now in use can deliver water at higher pressure than the reciprocating pumps heretofore used, and the pres- sure can be readily increased by adding to the number of stages or by running the centrifugal pumps in tandem, with- out affecting the structure or general efficiency of the pumping equipment. In order to obtain a maximum out- put with centrifugal pumps, high per- ipheral speed is necessary, The char- acteristics of the steam turbine make it especially valuable for this work, as it also is most efficient at speeds that are much higher than those obtained with any form of reciprocating engine. At present five boats equipped with Curtis steam turbine driven centrifugal - multi-stage pumps are in commission, distributed as follows: Two each in the fire departments of New York and Chicago, and one at Duluth, which was constructed for the Duluth, Missabe & Northern railway. In addition to these, two are now being built for the city of San Francisco, The pumping equipment of the New York and Chicago boats were described in the June, 1908, and Jan. 1909, edi- "tions of the Review, and the following refers only to the newer types exempli- fied by the boats designed for service in the waters about Duluth and San '. Francisco. The details of the equipment of these boats constitute in themselves. the Wetrongest argument for their adoption ry by every city having water front prop- ee which, in the event of fire, could Sa fe ae Be aki Lae 8 Lh