One of the greatest improvements for the benefit of commerce, made in the present century, is the employment of lenses, for reflectors in Lighthouses ; this has been acknowledged by the most scientific men of the age, and no man can doubt the fact who sees a lens light and a reflector in two different lighthouses. The application of the lens to other purposes than lig-hthouses would certainly be as great an improvement and benefit to the community—such as railroad lamps on locomotives, at switches, stations, &c. ; beacon lights, steamboat lamps, dock lamps, &c. ; and this has long been a desirable object by men of science, but Until recently it never was done, owing to the old expensive way oi making lens. The improvement now made is a grand one, and is the invention of John L. Gilliland, Esq., of the Brooklyn Flint Glass Co., for which a patent was granted on the 10th of last August. On page 174, this Vol. ot the Scientific American, we briefly described this invention, for which a patent was ta ken out in England in the name of Mr. Newton, the agent there, and not that of Mr. Gilliland—a system pursued in England which we do not approve. The improvement consists in moulding dioptric lenses of any size, or in sections, and making them of crystal. The dioptric lens heretofore in use for sea and other lights requiring great intensity, have been in rings made up in segments according to the diameter of the required lens. It has been pronounced impossible to produce accurate lenses of large size, made in one piece, and it has also been.pronounced impossible to make them of pure flint glass, hence crown glass has heretofore been exclusively employed in theFres-nal apparatus, and the "annular band lens," alone attempted. These two pronounced impossibilities are proved to be fallacies by that improvement. Lens of any size are made by Mr. Gilliland in one or more pieces, and of pure flint glass, thereby reducing the expense so much that this great improvemeet can not only be cheaply applied to light houses, but for all the varied purposes we have already enumerated. On page 174, while noticing this invention, we recommended it for dock lights to our ferries. Since that time one has been placed on the South Brooklyn Ferry Dock, and its brilliancy has astonished all who have teen it. Fig. 1 is a revolving dioptric apparatus of the first order for a lighthouse, and fig. 2 is a view of a locomotive lamp for railroads, with the new dioptric.lens cast in one piece. In fig. 1 the lenses are arranged around a central lamp placed on the level of their focal plane, and forming by their union a right octagonal hollow prism circulating round the fixed central flame, and showing to a distant observer suecejjife flashes of light. The action is simjll#f mirrors, but the Sashes of light .a3ijljB8 intense. Each lens subtends a ijtjBfMin''al pyramid of light of about 47*WHfation. beyond which limits the ieriticuiaflBftjii could not be advantageously pushe2jppng to the extreme obliquity of the ineidsnee of light ; but Fres-uel conceived the idea of pressing into the service of the mariner, by means of two very simple expedients, the light which would otherwise have uselessly eJ.;aped above and below the lenses. For intercepting the upper portion of the light, he employed eight smaller lenses of 19 68 inches ot focal distance inclined inwards towards the lamp, which is also their common focus, and thus forming by their union a irustrum of a hollow octagonal pyramid of 30 of inclination. The light falling on those lenses is formed into eight beams rising upwards at an angle of 50 inclination. Above them are arranged eight plain mirrors, so inc-lined as to project the beams transmitted by the small lenses into the horizontal direction, and thus finally to increase the effect ot the light. In placing those upper lenses, is is generally thought advisable to give their axes a horizontal direction of 7 or 8 from that of the great lenses, in the direction contrary to that of the revolution of a frame which carries the lenticular apparatus. By this arrangement, the flashes ot the smaller lenses precede those of the larger ones, and thus tend to eorrect the chief practical defect of revolving lenticular lights, by prolonging the light periods. F is the local point in which the flame is placed ; L L are large annular lenses forming by their union an octagonal prism, with the lamp in its axis, and projecting in horizontal beams the light which they receive from thg focus. L' L' are the upper lenses, forming by thir union a frustrum of an octagonal pyramid of 50 of inclination, and having their foci corresponding in the point, F.— they parallelize the raya of light which pass over the lenses. M M are the plane mirrors placed above the pyramidal lenses, L' L', and so inclined as to project the beams reflected from them in planes parallel to the horizon. Z Z are lower zones, substituted for curved mirrors. The lowerjrpar) shows the movable frame work, which carries the lenses and mirrors, and the rollers on which it circulates, with the cleek-work for giving motion to the whole. Mirrors or reflecting lights are open to tlje objectien of losing light by reflection and of being composed ot perishable materials as it regards their polish ; the plated silver convex concavo plates soon wear out by frequent polishing. The dioptric lens of Mr. Gilliland is made of imperishable materials, and its illuminating effect in comparison with a mirror is said to be as 140 isto 87—a great difference truly. We consider that making dioptric lens of moulded crystal, by which they can be produced at such a low rate as to be employed for the different purposes we have stated, is one of the most valuable inventions that has been brought before the public in a long time. There should bo an.tyajMsm system of signal lights adopted feBjBHHPlmbo&fei so that there can never ';)e'HHRe mac' *y one vessel respecting JRpfP'Ueh another is steering, such asJHiPfP "gM on the larboard paddle box, aKa red one on the starboard one, and a dekV brilliant lens light on th bow. This lens has been" applied to lanterm for hanging on the top mast of sail-ig vessels, and no one should be allowed at saa, or at anchor in a river to be without such a lantern. Every rear car of a railroad train ?hould have one of these lamps, in order to prevent being run into, as sometimes has been done by a following train when something detained the first one. The lamps and Ian-terns made with a crystal lens give a light which can be seen at many miles distant.— These improved crystal lenses applied indiffer-rent ways to lamp, like figure 2, for railroad, dock, and steamboat lamps, also to lanterns for steam and sailing vessels, can be aeen at the warehouse of the Brooklyn Flint Glass Co., No. 30 South William street, this city. We would state here that this American Company was awarded a prize medal at the World's Fair for the best flint glass that was exhibited there—it possessed a greater amount of brilliancy and purity of .color than any exhibited by the famous establishmertts of Prance Bohemia ad England.
This article was originally published with the title "Gilliland's Dioptric Crystal Lenses"