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A FAN OF GREAT VOLUME. ~ Mr. W. Carlile Wallace, known to a great many ship builders and ship ° owners of the United States on account of his connection with the Ellis & Eaves draft business of John Brown & Co. of Clydebank, is about to in- troduce in this country a centrifugal fan for which wonderful claims are made. It is known as the Sirocco fan. The patents are owned by David- son & Co., Ltd., of Belfast, a large engineering concern that has branches in London, Manchester, Glasgow, Bristol, Calcutta and Colombo. Mr. Wallace has about completed arrangements at the Schenectady works of the General Electric Co. for tests and an exhibition of the fans and the manufacture of them in this country will be undertaken shortly. They are long past the experi- mental stage. Thou- sands. are in use on the other side. The White Star . liner. Celtic is among large ships on which these fans have recently been installed. What. has _shitherto been generally accepted as best construction for technically as such in text books, is in Sirocco' centrifugal fans practically reversed on every point. The chief points of this re- versed construction may be summarized as fol- | a a ihe Sirocco ans the blades are very FIG. 1. PAN WHEEL, SIROCCO TYPE. "numerous with shieie radial measurement (relatively to the diameter of the fan) very shallow, and their axial measurement very long. Their outer edges are curved forward in, the direction of rotation, and the air passages between the blades are usually open at the ends towards the inflowing air. The inlet for admitting the air to the fan, and also the outlet for its discharge, are approximately of equal diameter to that of the fan itself. The practical effects of this new construction are that in these fans the volume of air discharged per revolution is from three to four times greater than in the best types of other centrifugal fans of equal diameter. The fan wheel, Fig. 1, is called the rotary member. It will be seen that the number of blades is large. There are in fact sixty-four, and a curious feature is that over a large range of sizes of fans this particular number of blades (sixty-four) appears to give the best results. It will also be _ noted that the blades are very short radially. Measured radially the blades are one-sixteenth of the diameter of the fan deep. Axially, however, the blades are long, three-fifths of the diameter, this dimension having been found to give the best results. The outer edges of the blades are bent _ forward, to a set angle, in the direction of rotation, and at one end they are slightly cupped. The inlet and outlet of the fan are approximately of equal area to that of the fan itself. It is claimed that the special form of blade employed, and its special size and shape, does away almost en- tirely with the detrimental and power-absorbing eddies which are so fre- quent with a number of other fans. Moreover, it is further claimed that the velocity of the air as it is discharged from the Sirocco fan is greatly FIG. 2. SIROCCO CENTRIFUGAL FAN, 25 INCHES IN DIAMETER. accelerated, so much so that it actually exceeds the peripheral speed of the blades by as much as 80 per cent. In this fan eddies are conspicuous by their absence. The intake draught of the fan is wonderfully regular, prac- tically not varying over the whole area of the intake. It is just as theceh a solid cylinder of air were being drawn bodily into the inlet, and ae velocity of the air appears to be absolutely the same over the whole area. In the matter of speed of discharge numerous tests have ane wa air to be 80 per cent. in excess of the rate of rotation of the tips of the ades. Fig. 2 is a Sirocco centrifugal fan of 24 in. diameter, overcast type, _ which Davidson & Co. show in one of their circulars and which was oy » jected to a-volumetric test (free intake and discharge) in gomparigon wit @ spirally-cased centrifugal blower fan of well known make. Re erring to this test the manufacturers of the Sirocco fan say: "In our fans the centrifugal' fans, . and, formulated | "1008 oh | _ MARINE REVIEW. 23 volume of air dealt with per revolution is relatively $0 great that the pas- sageway for same around the circumference of the fan requires to be equivalently large, consequently the casing or housing for the Sirocco is (relatively to the diameter of the fan wheel) much larger than in other centrifugal fans, the inlet and outlet openings to and from the Sirocco fan being about four times larger in area than those employed in other centri- fugal fans of the same diameter, and of which the blower fan used in this i is considered one of the most efficient." The report of the test is as ollows: pe ee SPIRALLY-CASED SIROCCO CENTRIFUGAL FAN VERSUS SPIRALLY-CASED CENTRIFUGAL BLOWER FAN OF A WELL-KNOWN MAKE. y Diam. Rev. Circumferential Air discharged of fan wheel per velocity in in cu. ft. in inches. minute. ft. per minute per minute. Sirocto fan 298g 25. "S95. 3,763 0 1G Centrifugal blower . 7.020, 24 600 3,768 8,250 Extra volume discharged per minute by Sirocco fan. ae 13,270 This shows in the Sirocco fan a volumetric discharge over 400 per cent. greater than that of the blower fan. - Pep VOLCANOES AND THE ISTHMIAN CANAL. The April earthquakes in Guatemala, by which it is now reported that 5,000 or 6,000 lives were lost, and the yet more appalling' catastrophe in the Windward islands, illustrate again the utter helplessness of the human creature and the futility of the strongest works of his hands, when assailed by the unknown forces of the globe's interior. This is the commonplace remark suggested by the recent earthquakes and volcanic furies. Is it not better to derive from these events, if possible, a lesson and a warning of some practical benefit to the people of this country and the world in general? The United States government is about to construct an inter- oceanic canal, Either congress or the executive will soon have to decide between the Nicaragua route and that by way of Panama: The danger of destruction to the canal by seismic disturbances is one of the recog- nized factors of the problem. The first report of the Isthmian canal com- mission discussed this danger, apportioned it about equally as between the two routes, and dismissed the possibility of canal destruction in this man- ner as a "risk which may be classed with that of a great conflagration in a city like Chicago in 1871, or Boston in 1872." The danger from direct volcanic activity, that is, from eruptions, was not considered by the com- mission. Martinique, however, has just shown the world what an awak- ened volcano can do. The Nicaragua route is lined with volcanoes, some of them having demonstrated the tremendous activity of the fires under- lying that part of Central America. It is sixty-seven years since Cose- guina, in the northwestern corner of Nicaragua, burst forth with an ex- plosion which lasted for forty-four hours. The noise was heard for 1,000 miles; the ashes were carried by the wind 1,400 sea miles from the crater. The mass of matter ejected in that eruption of Coseguina has been com- puted as great enough to have covered a surface equivalent to eight times the surface of France. The eminent French engineer, M. Bunau-Varilla, has estimated that during the forty-four hours of activity the output of stones and ashes every six minutes of the time was equal in volume to the total volume of the prism of the Nicaragua canal as calculated by the commission. That is to say, Coseguina poured out in six minutes what it would take the canal contractors eight years to excavate. Such another volcano in constant activity, with its last great eruption as recent as 1883, dominates the island in Lake Nicaragua which every ship will skirt on the passage from Greytown to Brito. This is Mount Ometepe. On the same island is a second volcanic peak, that of Madera. In 1844, seven years after the explosion of Coseguina, occurred the great earthquake which destroyed the city of Rivas, near the Pacific shore, and wrought great damage even at Greytown, 150 miles away on the Atlantic side. The line surveyed for the Nicaragua canal between the lake and Brito runs only 5 miles from Rivas. We now quote from M. Bunau-Varilla, who, although formerly engi- neer-in-chief of the Panama canal and therefore a partisan of that route, is entitled to be heard on any question of fact with the respect due to his personal character and professional eminence: "In Panama there is within a distance of 180 miles from the canal no volcano, even extinct. The Isthmus there, since its formation in the early quarternary period, before man appeared on the earth, has not been modi- fied. This is quite the contrary in Nicaragua, which has always been the site of seismic convulsions, whose lake was formerly a gulf of the Pacific ocean, and whose name was associated with the most terrible volcanic explosion ((\Coseguina) ever recorded in history before the Krakatoa ex- plosion. .It must be borne in mind that these terrible menaces would mean, if realized, not only the destruction of that costly canal, but the ruin of the immense interests on both sides of the Atlantic which will have been developed by the' great waterway and receive a death blow by its paralyzation. Nothing similar can be feared in Panama, as no trace of any volcanic activity may be found on that isthmus, whose rare and small seismic vibrations come from distant centers." A few days ago the question of volcanic menace seemed so remote as to be almost negligible in the consideration of canal legislation. To- day, on account of the impressive demonstration made by Pelee and Morne Garu, that question merits and should receive in congress the most careful attention--New York Sun. The McClintic-Marshall Construction Co. of Pittsburgh, builders of iron and steel construction work, have received a contract from the St. Clair Furnace Co. for a great steel railroad trestle which is to extend from the level of the terminal railroad system of the St. Clair works at Clair- ton over the steel storage ore bins from which the furnaces are to be directly fed with iron ore. The trestle will be 360 ft. long with twelve separate spans. Extending from the trestle overhead will be a number of tracks frem which the ore in steel hopper railroad cars will be dumped "to the steel. bins;- These bins will discharge the ore into small hoppers which will be carried by the conveying system of thé Brown Hoisting Ma- chinery Co. of Cleveland to the furnaces. The contract for this bridge has been placed with the American Bridge Co.