Natural light should be secured if possible for every room. Windows should be frequent and extend well up toward the ceiling terminating in a straight line so as to afford large supply of light from the top. Windows like those in an ordinary house or office building, coming within two or three feet of the floor are more satisfactory both for inside and outside appearance than those which leave a high blank wall beneath them. From the street a blank wall has a prison-like effect; on the inside it cuts off communication with the rest of the world and the impression is unpleasant. The proper object of library windows six or eight feet above the floor is to allow unbroken wall space for book shelves beneath them. There is no serious objection to this at the back of the room or sometimes at the sides of the house where the windows are not conspicuous from the street, but every room of any size, if it is next to the outer wall, should have windows to look out of on at least one side.
A book room at the back of a building may secure excellent light from side windows eight feet above the floor with lower windows at the back.
The lighting of large interior rooms is often a difficult problem. Light will not penetrate to advantage more than 30 feet. Skylights, domes and clerestory windows are used. In the case of the dome or clerestory the room to be lighted must be higher than those immediately surrounding it. The clerestory plan with upright windows is most satisfactory when available, being cheaper and giving better security against the weather than the skylight. In a large building with interior courts, the lower story of the court is sometimes covered with a skylight and used as a room.
This appears in the plans for the New York Public and the Utica Public libraries. Skylights must be constructed with special care to protect rooms against the weather.
The problem of light is peculiarly difficult in the crowded blocks of cities. A library front may sometimes touch the walls of adjoining buildings so that light can enter only from the front and rear. If extending more than 40 feet back from the street, it will be necessary to narrow the rest of the building so as to leave open spaces on each side, or to introduce a little light by the device of light wells. Occasionally a large city library is found on the upper floors of an office building, where light and air are better than below, and the cost of accommodation is less. The use of elevators makes this feasible.
Shelving.
The general scheme of book shelves should be fixed before the plan of the building is drawn. Otherwise the space for books can not be determined and serious mistakes may be made. Between the two extremes of open wall shelves and the close stack a compromise is necessary. The large library will put the bulk of its books in a stack and bring a considerable selection of the best books into an open room. The small library will begin with books along the walls and provide cases for additions from time to time as needed. Its patrons will enjoy at first the generous spaces of the open room without an array of empty cases to offend the eye and cumber the floor. When walls are covered with books a floor case will be introduced and others when needed will be placed according to plan, till at last the floor is as full as it was meant to be, and the basement beneath having served for a time to hold the overflow, a second story of cases is put on the top of the first. This process should be planned in advance for a term of 20 years.
For public access passages between cases should be five feet wide. Cases have sometimes been set on radial lines so as to bring all parts under supervision from the center. This arrangement, specially if bounded by a semi-circular wall, is expensive, wasteful of space and of doubtful value, except in peculiar conditions. It is not adapted to further extension of the building.
Size of shelf.
For ordinary books in a popular library the shelf should not be more than eight inches wide with an upright space of ten inches. Eight shelves of this height with a base of four inches and crown finish of five inches will fill eight feet from the floor and the upper shelf may be reached at a height of 81 inches or six feet nine inches. Ordinary shelves should not exceed three feet in length. A length of two and a half feet is preferred by many. A shelf more than three feet long is apt to bend under the weight of books. For books of larger size a limited number of shelves with 12 inches upright space and a few still larger should be provided. The proportion of oversize books will vary greatly according to the kind of library, a college or scientific collection having many more than the circulating library. Any reference room will contain a large number of such books and its shelves should correspond.