=Lighting.=--No point was more carefully studied in the construction of the stacks than the lighting. Preliminary plans requiring an immense amount of labor were made, showing the amount of direct sunlight which any portion of the three arms would receive at any hour of the day, any month in the year. Skylights along the line of the corridors help light the upper tiers. The walls are honeycombed with windows from top to bottom. In the north and south stacks there are no less than three hundred and sixty. They occur at the ends of the passageways between the ranges, being placed at the intersections of the decks, so that each may diffuse direct light into two tiers at once. In this way there can be no perceptible difference in the amount of light cast into the upper and lower portions of the tiers. At the end of each passageway the window is fitted with a seat for the use of the readers admitted to the stacks, or attendants. Ground glass is employed for the windows on the east side of the south stack, where the sunlight is so abundant and continuous that it would be inconvenient if admitted, besides being likely to cause the bindings of the books to fade; everywhere else the clear open plates invite the entrance of all the illumination which can be obtained. Each window consists of a single piece of polished plate glass three feet wide, and permanently sealed, so that no dust or moisture can ever penetrate it. In order to wash the glass from the outside the wall is fitted at convenient intervals with skeleton galleries. The courts themselves give an abundance of full, bright light; and that none of it may be wasted, and in order that it may be evenly distributed through the tiers, both at the bottom and top of the stacks, the walls of the courts are constructed of yellow enamelled brick, which makes an admirable reflector, on rainy as well as on sunny days. Inside, the marble decks are highly polished, so that they, too, serve as efficient reflectors, casting the light which they receive into every nook and cranny of the stack. Evenings, the light is furnished by incandescent lamps, with which the passages and corridors are abundantly equipped, and here again the polished decks serve a most useful purpose in diffusing the brilliant illumination throughout the whole system of shelving. Altogether, it may be very confidently stated that no great collection of books was ever before so thoroughly and conveniently lighted, whether in the day or at night. THE LANTERN.