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- : MARINE REVIEW. POWERFUL LIGHT FOR AN OLO TOWER. INTERESTING STRUCTURE REPRODUCED AT THE GLASGOW INTERNATIONAL EXPOSITION--DESCRIPTION OF THE LIGHTING APPARATUS. [Special correspondence to the Marine Review.] Glasgow, Scotland, June 12--One of the most striking features of the Glasgow International Exposition is a reproduction of the Bell rock light- house. The structure, of course, is only temporary, but the lantern, lamps and machinery are the actual plant for the actual light-house on the Bell rock on the east coast of Scotland, some 12 miles from Arbroath. It stands on a dangerous reef which is little more than awash at low water and is covered to a depth of 10 ft. at high water. This rock was first lighted in 1811, the tower taking four years to construct. The tower and appara- tus were designed by Robert Stevenson, engineer to the commissioners of northern light-houses, and executed under his direct superintendence. It is now the oldest existing light-house tower in Great Britain, and shows no signs of the weakness which has appeared im other towers. Although the tower is still quite equal to its purpose, the lantern, and machine, which are about ninety years old, show signs of needing renewal, while both they and the apparatus are an- tiquated, and the light is too weak in power for such an important place. The commissioners of northern light- houses accordingly instructed Messrs. Steven & Struthers, Glas- gow, to construct the lantern and. machine now shown to the design of Messrs. D. '& :€s"Stevenson,. C.E., Edinburgh. 2 The optical apparatus has been specially designed to suit the peculiar | circumstances. The light has to be maintained of its existing char- . acter, namely, a red and white flash alternately, and of a maximum power consistent with one of the beams being red.' It is somewhat of the bivalve type, but differs largely from anything yet constructed. It is a combination of two orders--hyper- radiant and first order. The white flash consists of 40° of.a hyper-radi- ant, the light from which is supple- - mented by back prisms of a size never before attempted. The red flash consists of 40° of hyper-radiant, the light being 'intensified by totally reflecting prisms subtending 145°. As the red glass shades abstract a por-' tion of the rays by absorption, the red flash is further intensified by di- optric mirrors of the best type. The glass work has been made in Paris by Messrs, Lepatite et Cie, but is not of French design, as might naturally have been supposed. The flash. will be about 112,000 candle power and is thus about five times the power of the most powerful red light of any French design. ~ The profiles of the prisms are de- signed for an index of refraction of 1.53 and the glass is set in a strong gun metal framing. .-The whole face of glass through which: the parallel rays from the burner are sent pre- sent a surface of no less than 9 by 9 ft., or 81 sq. ft. of focal opening, Vhe apparatus stands on a cast iron table, which is made to revolve on conical steel rollers with ball bearings, be- tween steel rings, by a circular rack and pinion driven by a clock ma- chine. Anti-friction roller bushes and ball bearing bushes are used in the 'construction of the different journals. The fly shaft makes 200 revo- lutions per minute and absolute regularity of the machine will be attained when fitted at the light-house by means of the governing fans. The burners are six-wick patent Doty burners and are supplied with paraffin oil forced up by a pump driven off the main gear of the revolving machine. The apparatus is enclosed in a lantern 18 ft. 6 in. diameter, to be erected on the tower at the Bell rock after the existing lantern has been removed, The lantern is sixteen-sided. The sash frames and astragals, which are triangularly made and thus of the strongest form, are made of gun metal of such a proportion of parts as to attain a strength of 16 tons per sq. in., with an extension of at least 6 per cent. The frames are glazed with polished mirror plate glass. The dome is of sheet copper of a spherical shape, surmounted by a ventilator to secure a proper draught and exclude the severest storm. The lightning conductor is 34 in. diameter and will be connected to the existing lightning rods of the Bell rock. for the tower was originally protected by a lightning rod inside as well as outside, so that all metallic bodies are in metallic connection. The fog signalling arrangement at the Bell rock will be maintained as at present, being an explosive signal of tonite fired by an electrical battery designed so that the signal cannot be fired until the charge is raised to the top of the lantern. : Messrs. Steven & Struthers also exhibit in the tower of the tem- porary light-house specimens and photographs of the large bronze cast- ings of which they make a specialty, including sterns, sternposts pro- peller brackets, rudders, etc. Some of these castings weigh 20 tons." From a drawing by Nicholas J. Quirk, Chicago. THE LAWSON YACHT INDEPENDENCE. [June 20, Specimens of their high tension "Marine" bronze, now largely adopted for propellers, are also on view, showing the high tensional and bending strains which this metal can resist. A breaking strain of up to 32 tons per sq. in., with an elongation of 30 per cent. on a length of 2 in., is regularly obtained from a bar 1 in. in diameter, and a bar of this diameter can be bent round a radius of 1 in. NOVA SCOTIA AS A PIG IRON MAKER. (From the London Statist.) A notable event in the iron world, and of great interest otherwise, is the arrival in the Clyde this week of a cargo of 3,500 tons of pig iron from Canada. The quality corresponds with Cleveland iron, and is there- fore suitable for foundry purposes. It comes across, we understand, at a freight of 10s. per ton, which is about the equivalent of half the bounty on export granted by the Dominion government; and it incurs landing and other charges amounting to 5s. per ton, which closely approximates the cost of taking Cleveland iron to Scotland by sea. This Canadian product then enters into direct competition with Cleveland iron, which, again, displaces Scotch ordinary iron--at a price. The price at which the Canadian iron has been sold has not yet been disclosed, but Cleveland warrants are just now 8s. 6d. per ton under Scotch G. M. B., which is considerably more than the normal difference, so that the moment of arrival is not very opportune from the Canadian point of view. The shipment marks a strange re- versal in the current of trade, for Canada has been in the habit of tak- ing about 10,000 tons of pig iron per annum from us, notwithstanding the contiguity of the United States. But it marks more than that. This iron comes from Cape Breton, Nova Sco- tia, where have just been completed four large blast furnaces for the smelting of iron ore conveyed at a low rate of freight, and' on a short sea run of twenty-four hours or so, from the iron mines of Newfound- land. These mines are near the sea- board and are cheaply worked, so that the ore is one of the cheapest ironstones in the world. It is con- veyed to Sydney, Cape Breton, for a fraction of the cost of conveying ironstone from Lake Superior to Pittsburgh, or from Bilbao to Mid- dlesbro' or Glasgow, and the fur- naces in which it is smelted are right on a rich and cheaply worked coal field on the seaboard. Here are be- ing erected a plant of some 400 coke ovens, and works for the manufacture of steel on a great scale. At Cape Breton the cost of the materials for the manufacture of a ton of iron is said to be only 3s. 3d. per ton, as against 13s. per ton at Pittsburgh. The peculiar advantages under which this new Nova Scotian enterprise is being started are well understood in the United States, and the knowing ones in the trade there have for some time been predicting that the cheap- est iron and steel in the world will in the future be produced in Canada. As to this we know not, but it is very evident that the first cost of iron smelted on the seaboard, with coal* requiring no transport, must be much lower than anything the United States can show under present con- ditions of working. Whether it will pay Nova Scotia better to export pig : iron than to turn it into steel is an- other question. The one disadvantage under which Cape Breton must suf- fer is in the matter of freight, for we do not know what cargoes large steamers can get to induce them to go there for return cargoes of iron, and to go there in ballast must be, of course, to enhance the outward freights. In the meanwhile, however, it must pay the smelters handsomely one pigs, because of the bounty, which bounty has been extended to Sydney, C. B., in two years has increased its population nearly four- fold and is already called the Pittsburgh of Canada. It promises, also, to be the rival of our Middlesbro' and Birmingham. From a provincial village it has been converted into a busy manufacturing town. Iron smelting is not quite a new thing there, but nothing has before been at- tempted on the present scale--favored in every way by the municipality, sanctioned and supported by the state legislature, and endowed by the Dominion parliament. Up till now Canada has not made more than about 90,000 tons of pig iron per annum. The new plant is equal to about 200,000 tons per annum. This, of course, is a small thing compared with the United States, or with Cleveland, and is not very large even compared with Scotland. But it is only the beginning of an industry of immeasur- able possibilities. This pioneer cargo sent to the Clyde may mark the beginning of a new epoch. The difficulties attending the supplv of ore for our blast furnaces seem to become greater year by year. It is pleasanter to have to look to Canada for future supplies of crude iron than to the United States, even though the enterprise at 'Cape Breton is being de- veloped at present by United States capital.