of the year, being, I infer, as unfortunate in this respect as our northern Atlantic or our Pacific coasts. in Scotland. Neither have the Scottish Board any light-ships, nor in- No light-ships deed is there any occasion for them, the coast being everywhere abrupt with no outlying shoals or reefs. Mr. Stevenson gave as his opinion, derived from observations, that revolving lights should be used as much as practicable for light-ships, for the reason that they have a greater range of visibility than fixed lights. Adoption of the jeet to the orders Trade. Messrs. Stevenson and Cunningham confirmed the statement made to me by Captain Doty in London, viz, that the Doty lamp, submineral oil lamp invented by the latter had been adopted of the Board of by the Scottish Board, subject to the approval of the Board of Trade, and with the understanding that he should receive as remuneration for his patent the saving effected in one year at each light-house where it might be introduced. At the time of my visit, however, it had been actually introduced into but five light-houses, as the Board of Trade hesi tated at the terms of Doty's offer, which would give him for the use of his patent about £75 ($375) for each firstorder light-house, and proportional amounts for smaller lights. The Board of Trade, acting under the advice of Trinity House, directed that the substitution of mineral for colza oil in Scotch light-houses should be deferred until the experiments on the relative values of the Trinity House (Douglass) and the Doty lamps should be completed; in order, I presume, to avoid paying a royalty to Doty if the Douglass lamp should be found superior or equal to his.* the report of In this connection I quote, from a parliamentary paper Extracts from in my possession, the following extracts from a report made Messrs. Stevenin 1870, before the adoption of mineral-oil in British light-son. houses, by the Messrs. Stevenson, engineers of Scottish lights: Flame pro duced by paraf "1st. The paraffine-flame produced by the four-wick mechanical lamp is 2 inches in height, and of great purity fine. and intensity. "2d. There is no difficulty, or even trouble, in maintain Care necessary ing the flame. "3d. According to those in charge, the light is, on the whole, more easily attended to than that from colza-oil. "4th. The same wicks have been used throughout the whole thirty days' experiments, and are still quite fit for use. * The Board of Trade have since given its authority for the substitution of mineral-oil in all of the Scottish light-houses. Wicks. "5th. The lamp-glass used for the experiments has stood during the month without breakage. "6th. The ordinary ventilation of the light-room has been found quite sufficient. "7th. No inconvenience has occurred from smoking of the wick or smell of the paraffine. "8th. No undue rise of temperature of the light-room or apparatus has occurred. "9th. The temperature of the paraffine in the cistern of lamp did not, after twelve hours' burning, rise above from about 550 to 63°. แ Flashing-point. "10th. The safe vaporizing temperature, or that to which Young's paraffine may be heated without giving inflammable vapor, as tested by us with Mr. Rowat's patent instrument, is about 140°. Quantity consumed. Cost, "11th. The quantity of paraffine consumed in the firstorder light was at the rate of 718 gallons per annum. The consumption of colza-oil is about 800 gallons per annum. "Taking the cost of colza-oil at 34s. per cwt., (2s. Id. a gallon, 683 cents,) which was the price in 1869, adopted in our recent reports on illumination by gas, and paraffine at its present price of 18. 4d. (33 cents) per gallon, we find that the cost of maintaining a first-class light with colza and paraffine will be £110 ($550) and £47 178. 4d. ($239.33} respectively, thus giving a yearly saving on each first-class light of £62 2s. Sd., ($310.66} ;) but if we take the present contract rate of colza of 38s. 6d. per cwt., (38. 1d. per gallon, 77 cents,) the saving would amount to £75 9s. 4d., ($377.33.) On the supposition of paraffine being used for all the lights under the charge of the commissioners, the Arnual saving. saving, calculated on the same basis, would amount to about £2,874 ($14,370) per annum, but at the present contract rate of colza the saving would amount to £3,478 158. id. ($17,393.891) per annum. "We have perfect confidence in recommending the use of paraffine for light-house illumination. Its introduction would require to be done gradually; the light-keepers would require to receive some instructions in its use, and a slight alteration would in each case require to be made on the level of the burner with reference to the optical axis of the apparatus, and the marks for testing the adjustment of the lamp to be carefully altered. A full set of directions would also require to be drawn up and furnished to all the stations when the change is made." permanence in ice. No more convincing proof of the utility of permanence Good results of in the peculiar service of light-house administration can be light-house servgiven than the excellent reputation the Scottish lights bear throughout the world for economy and efficiency, and it is well known that the Commissioners are eager to adopt any improvement which tends to the increase of either. Mr. Cunningham has for many years most ably filled the position of secretary, and for nearly a hundred years the Stevenson family has supplied engineers. The time at my disposal was too limited to allow me to visit any of the Scottish light-houses, and I especially regretted that I could not accept Mr. Stevenson's invitation to visit Bell-Rock light-house. My thanks are due both to Mr. Thomas Stevenson and Mr. Cunningham for their polite attentions while I was at Edinburgh. THE MANUFACTORY OF DIOPTRIC APPARATUS FOR LIGHT- On my return to London from Edinburgh I visited the extensive glass-works of Chance Brothers & Company at Spon Lane, near Birmingham, in compliance with an invitation which I received from Mr. J. T. Chance soon after arriving in England. This establishment is most extensive, and is mainly devoted to the manufacture of plate-glass, which is sent from here to all parts of the world. A part of the works is, however, devoted exclusively to the manufacture of apparatus for light-houses, a manufacture commenced by this firm in 1855, in competition with the lens-makers of Paris, who until that date monopolized this branch of industry. rep lishing the manufacture of lighthouse apparatus. Mr. Chance stated that in establishing this part of their Cost of estabtrade they had lost more than $100,000, but that their utation is now established, and they supply not only Great Britain, but many other countries, with lenses, lanterns, lamps, and accessories of all kinds necessary for the service of lights. polishing prisms. They have in use a great variety of machines for grinding Machines for and polishing the prisms, and the establishment appears to be as complete in every particular as any which I saw at Paris. The scientific branch of this industry is in charge of Dr. Hopkinson. Dr. Hopkinson, who is responsible not only for the correctness of the forms of the various parts of every optical apparatus, but for their correct assembling, and he personally tests each lens before it leaves the manufactory. Flashing-lens for Start Point. Red cut to be produced. Apparatus for house. Among other works in hand, I saw a revolving lens of the first order for the light-house at Start Point, on the coast of Devonshire, remarkable for having flash-panels that cover arcs of 60°, which is larger than any before attempted, as far as I am informed. Heretofore the arcs of first-order lenses have not extended 45°, and as the amount of light in the flashes is nearly in proportion to the size of the panels, it follows that the power of this lens, when compared with those of similar character heretofore made, is nearly as 3 to 2. A red cut showing the position of outlying rocks near Start Point, will be produced, as is done at the electric lights at Souter Point, by collecting a portion of the rear light and throwing it down a tube to a lower light-room upon a set of totally reflecting prisms, which in turn bends the beam and turns it out upon the sea. A new first-order dioptric apparatus for Longships lightLongships light-house, on the coast of Cornwall, was also in progress, and I had the pleasure of witnessing Dr. Hopkinson's final test of the accuracy of this lens. Dr. Hopkin The doctor also kindly presented me with a photometer, son's photometer. of his own invention, for comparison of lights at a distance, which is designed to be free from the defects inherent in those depending on absorption. It is very compact, and consists of two Nicol prisms, which can be moved relatively to each other in azimuth. A little tube carries both the analyzing prism and a second tube containing the polarizing prism. The latter being turned till the light, which is viewed through the axis of both prisms, is eclipsed, the angle through which the polarizer is moved, is read. The other light being then observed in the same way, a comparison of the angles gives the relation of the powers of the lights. For many years the place now occupied by Dr. Hopkinson was filled by Mr. J. T. Chance himself, and to him the service of light-house illumination is indebted for several treatises on the subject. THE LIGHT-HOUSES OF FRANCE. THE COMMISSION DES PHARES. I arrived at Paris on Saturday, the 5th of July, and on the 7th I went to the offices of the Commission des Phares, or Light-House Board of France, situated on the hill Trocadéro, which overlooks the Seine and the Champ de Mars. This French Light Board is composed as follows: Four engineers, two naval House Board. officers, one member of the institute, one inspector-general of marine engineers, one hydrographic engineer. The executive officers of the establishment at Paris are M. Léonce Reynaud, Inspector-General of the Corps of Engineers des Ponts et Chaussées, who is Director of the French light-house administration, and M. Allard, engineer of the same corps, and Engineer-in-Chief and Secretary to the Commission. The entire administration on the seaboard is in the hands Light-house administration. of the engineers, who, in addition to other duties, are charged with the work of river and harbor improvements. At the time of my visit to the Dépôt des Phares, M. Reynaud, who is, I believe, much occupied with other duties, especially at the École des Ponts et Chaussées, was absent, but I had the pleasure of meeting M. Allard, upon whom the major part of the executive duties devolves. During my long interview with M. Allard, he kindly showed me the different parts of the establishment at Trocadéro, all of much interest, particularly the grand hall or council-chamber of the Commission, the museum, the experimental rooms, and store-rooms. phares. The buildings are placed around a rectangular court-yard Dépôt des in which are models of light-houses, buoys, &c. Tower for ex The principal building, which contains the offices of the commission, is a handsome structure 150 feet long and two stories in height, built of brick and limestone in alternate courses. It is surmounted by a tower and a first-order lantern, where experiments are made, and from which a mag-periments. neto-electric light is exhibited on occasions of public display; as, for example, the fête nocturne in the Champ de Mars, in honor of the Shah of Persia. This fête M. Allard was kind enough to invite me to witness from the Dépôt des Phares, which afforded a most desirable site from which to view the magnificent spectacle. The grand entrance hall also contains many models, and those of the rock light-houses of France at once arrest the attention of the visitor. The council-chamber of the commission is richly decorated, and upon its walls are painted two large charts, each occupying an entire side, one of the world, on Mercator's projection, showing all the lights now in existence, thus, as M. Allard happily observed, marking the progress of civilization in a most striking manner. The other chart was one of France, showing not only its lights, but the illuminated areas. ber. Council-cham |