The "Sciopticon," is the name of his new instrument, and from actual trial we find that it possesses many superior qualities. Its lenses are excellent, and in illuminating power its light ranks next to the oxy-hydrogen. The sciopticon light is produced from ordinary coal oil by an ingenious arrangement of double flames, intensifying the heat and resulting in a pencil of strong white light. Prof. Marcy's instrument is the perfection of convenience, simplicity, and safety. Any one may successfully work it and produce the most brilliant pictures upon the screen. It is peculiarly adapted for school purposes and home entertainment. Those who wish to do a good thing for young people should provide one of these instruments. Photographic transparencies of remarkable places, persons, and objects, may now be purchased at small cost; while there is no end to the variety of pictures which may be drawn by hand at home upon mica, glass or gelatin, and then reproduced upon the screen by the sciopticon. * * * * * The Largest Well in the World--Capacity 1,000,000 Gallons of Water per Day. One of the grand necessities of the Prospect Park, Brooklyn, N.Y., that of providing for a continual supply of water for all the purposes of the Park developed itself, as the Commissioners progressed with their stupendous undertaking. Mr. Stranahan, the President of the Board, after carefully weighing the cost, the practicability, and importance of having an independent water supply for the Park, advised the Commissioners of the plan which had suggested itself, and the calculations which had been made by the engineers relative to the project, and the work was commenced, the first idea being to secure at least a partial supply of water by means of a well constructed in the Park. The subject was thus treated in the last annual report of Mr. C.C. Martin, the engineer in charge: "This well has been located on the south side of Lookout Hill, near the lake, and work was commenced upon it late in the season. After a careful consideration of various methods for sinking the well, it was decided to build the wall and then to excavate the material from within, trusting to the weight of the wall to force it down. Sixteen feet of the wall were laid securely bolted together, before the excavation was commenced. A derrick with a boom fifty-five feet in length was set up near the wall, so that the sweep of the boom commanded the interior of it. Iron buckets containing fourteen cubic feet each were obtained, and a six-horse power hoisting engine purchased. With these appliances the excavation was commenced, and carried on with slight interruption until the work was suspended on account of the frost."