“Broken” floors are used in some libraries, the Massachusetts State Library, for instance; one stack floor being three and one-half feet higher and the next one three and one-half feet lower than the corresponding building floor, on the idea that it is easier to go up or down half a flight than a whole flight, for anyone wanting to get books. But isn’t the average the same? In this form, the very great convenience of moving books by trucks is sacrificed, so that the almost universal custom is to have the ground floor, and every second floor above, level in the stack with floors in the building, thus fixing the height of the latter at fourteen or fifteen feet, except the top floor, which is free, and the basement, usually determined by other exigencies.
The material used for “decks” may be openwork iron, marble, or more usually translucent ground glass.
The floor of the stack as well as of the building basement, is generally cemented, with special provisions for excluding dampness.
Passages. Those running lengthwise may be called gangways, those across between cases, aisles. The number of gangways varies with the size and use of the stack. Although it might be built without a center gangway, and have one on each side, or only on one side—it would then be a very narrow stack—the usual construction is to have a gangway about four feet wide down the center, and one of less width (just enough to allow passing around, say two feet,) at each outer end. But if it is desired to have very close packing, these side gangways may not be necessary. In building the new Salem stack, Mr. Jones decided that he could so run the classification of the books from the center around back to the center, in every aisle, that there would be little need of passing around the outer ends, and he could omit them and so gain that much more for books.
The center gangway may be any width desired, but should of course be wide enough to serve as thoroughfare for men, book-trucks, and boxes. Although four feet seems the average width, it varies from three feet to six feet in existing libraries. Good, large windows on each floor should light gangways at the far end.
The length of aisles varies with the width of the stack building, though limited by the belief that no bookcase should be more than 15 or 18 feet long, which requires other gangways at that interval. The width of the aisles has varied. The original Harvard width, 2 feet 4 inches, appears to be the very narrowest which will allow passage of two persons, or stooping to the lower shelves; 2 feet 8 inches is very common; 3 feet is so roomy that the stack becomes convenient for limited open-access; while 5 feet “on centers” (3′ 6″ or 8″ aisle) is the maximum in stacks at present.
Many stacks have wide intervals at the sides of the “deck” in each aisle—so wide as to have to be wired to prevent books falling through—“for ventilation, diffusion of light, and communication,” but such wide spaces are not needed for light or ventilation, and are much handier for dropping pencils than for passing books, so that I prefer wider decks with small rims for protection, and much narrower spaces along the cases.
Stairs. Stack stairs need not be wide, for they are so short that two people never need to pass. Two feet wide is enough. When first adopted, circular stairs were used, as supposed to occupy less space, but they were found to be inconvenient and dangerous, and since measurement has shown that straight stairs need occupy no more space, the “cork screws” have been entirely superseded. Eight-inch risers and 9-inch treads are recommended by Champneys,[296] who thinks, by the way, 2 feet 4 inches the right width, iron with rubber treads being the material.
Stairs should be put in wherever they will be most convenient, and where they interfere least with book storage and passing. One flight certainly should be next the entrance on each floor, and one flight generally at the other end. If they be set sideways in the folio shelving there, which is not always all needed, they seem to interfere least. (See paragraph on circular or winding stairs.)
Lifts. Light lifts for single books, or few books at a time, are needed for all stacks (See that title, on [page 228].) In large libraries and high stacks, elevators large and strong enough to carry trucks and boxes, are also necessary. For lifts, hand operation will serve, or electricity; for freight elevators, some sort of power is better.