The necessity for a superior illuminating arrangement was at once experienced, and attention was given to the lamps that were fed with the mineral oils, instead of animal or vegetable oils. Although various forms of mineral oil lamps were tried, they were not successful, until Mr. L. Marcy, of Philadelphia, conceived the idea of constructing a lantern sufficiently small to make one chamber serve as the lantern and the lamp. He used for his wick two flat cottons parallel to one another, with the tops almost in contact, and the edges of the wicks turned towards the condenser. This lamp he charged with mineral oil, and thus obtained an instrument surpassing anything of the kind previously constructed.
Since then many improvements have been made, each modification receiving a distinctive title. We have thus ‘The Silber Light,’ ‘The Triplexicon,’ ‘The Duplexicon,’ ‘The Refulgent,’ ‘The Euphaneron.’ It will not be necessary to explain each of them in detail, as they have many things in common, and it will suffice to describe ‘The Euphaneron,’ which is perhaps the best of the series.
The Euphaneron (that which shows well) differs in several important particulars from the phantasmagoria lantern. The body of the lantern (which serves to support the condenser and objective) is made of Russian plate iron, which neither rusts nor blisters. The condenser consists of two 4-in. lenses of the form we have already described, and the objective is a double achromatic combination. The outer lens of the objective, designated the ‘front lens,’ is in form a plano-convex lens. The inner lens, called the ‘back lens,’ consists of two separate lenses, one an unequi-convex lens, the other a meniscus-concave lens. This combination gives a beautifully-defined picture on the screen, with flatness of field and abundance of light.
The lamp is entirely distinct from the body, and will burn equally well either outside or inside the body of the lantern, the chimney being attached to the lamp and not to the body. The cistern of the lamp forms its base, and is filled with mineral oil. From the top of the cistern rise two rectangular tubes, sloping together as they rise; these contain the two wicks. The wicks do not stand parallel to each other, but form an acute angle with the base of the triangle towards the condenser, and this is the peculiarity that brings about the equal illumination of the disc. The wicks are raised and depressed by the action of two milled heads at the back of the lamp. Now, instead of surrounding the flames with a glass chimney, as is ordinarily the case, a metal combustion chamber is provided, and to this chamber the chimney is attached. The ends of the chamber are open, the front being closed by a glass plate, the back by a silvered reflector. Attempts have recently been made to add a third wick to this lamp, but they have not been very successful, the lantern being rendered very much hotter without affording a corresponding gain in brilliancy. The Euphaneron exhibits photographic slides in a most satisfactory manner on a disc 10 ft. in diameter. The disc is uniformly illuminated, and the picture well in focus all over the screen.
Directions for trimming the Euphaneron Lamp.—Remove the lamp from the lantern, carefully clean the front glass and the mirror. Turn back the combustion-chamber on its hinge, so as to expose the tops of the wicks. These should be cut quite smooth and straight, without any projecting filaments. The cistern should be nearly filled with the best mineral oil, and the wicks turned up a little way and lit. The combustion chamber should be now restored to its place, the lamp put into the lantern, and the chimney fixed on. The wicks should then be gradually raised as high as they will bear without smoking. In putting the oil into the lamp care should be taken not to spill any on the outside. The general directions already given for showing the pictures are then to be followed in using the Euphaneron.
5.—DISSOLVING VIEWS.
The lanterns that we have hitherto been describing have been those capable of exhibiting single pictures only; we have now to explain the production of dissolving views.
Fig. 4.