_Extension._ To meet the needs of a rapidly growing library it is important at the beginning to fix the lines of extension. A building with a front of two rooms and a passage between may add a third room at the rear, and at a later stage, add a second building as large as the first and parallel to it, the two being connected by the room first added. This is the architect's plan for the Omaha Public Library. _Open court._ When a library is so large that one book room is not enough, two such rooms may be built to the rear, one from each end of the building with open space between, and these two wings may be carried back equally and joined at the back by another building, thus completing the square around an open court. This gives wide interior space for light and air, or grass and flowers. Such is the plan of the Boston Public and Princeton University libraries. It will be the same in Minneapolis when that library is complete. In the plan of the new library at Newark, N. J., the central court is roofed over with glass becoming a stairway court with surrounding galleries opening on all rooms. In Columbia University, New York, as in the British Museum, the center is a great reading room capped by a dome high above the surrounding roofs and lighted by great clerestory windows. If the street front is very long there may be three extensions to the rear, one opposite the center and one from each end, leaving two open courts as in the plan for the New York Public or the Utica Public; and this general scheme may be repeated and carried still farther back leaving four open courts as in the Library of Congress. This plan can be extended as far as space can be provided. When the general plan of the large building is fixed, passages will be introduced, parallel to the front and sides, and departments will be located as may be judged most convenient, always having regard to the convenience of the patrons of each department in finding ready access to the books they need and providing for supervision and attendance at least cost of time, effort and money. Extravagance in library building is not so often found in lavish ornament as in that unfortunate arrangement of departments which requires three attendants to do the work of one or two. _Light._