e material for the outside walls may be
brick or stone, according to taste or relative cost. Brick is good
enough, and if of the best quality, and treated with stone trimmings, is
capable of sufficiently ornate effects, and is quite as durable as any
granite or marble. No temptation of cheapness should ever be allowed to
introduce wood in any part of the construction: walls, floors, and roof
should be only of brick, stone, iron, or slate. A wooden roof is nothing
but a tinder-box that invites the flames.

In general, two stories is a sufficient height for library buildings,
except in those of the largest class, and the upper floors may be amply
lighted by sky-lights. The side-lights can hardly be too numerous: yet I
have seen library buildings running back from a street fifty to
seventy-five feet, without a single window in either of the side walls.
The result was to throw all the books on shelves into a gloomy shade for
many hours of each day.

The interior construction should be so managed as to effect the finding
and delivery of books to readers with the greatest possible economy of
time and space. No shelves should be placed higher than can be reached by
hand without mounting upon any steps or ladders; _i. e._, seven to seven
and a half feet. The system of shelving should all be constructed of iron
or steel, instead of surrounding the books on three sides with
combustible wood, as is done in most libraries. Shelves of oxidized metal
will be found smooth enough to prevent any abrasion of bindings. Shelves
should be easily adjustable to any height, to accommodate the various
sizes of books.

In calculating shelf capacity, one and a half inches thickness a volume
is a fair average, so that each hundred volumes would require about
thirteen feet of linear shelf measurement. The space between uprights,
that is, the length of each shelf, should not exceed two and a half feet.
All spaces between shelves should be 101/2 or 11 inches high, to
accommodate large octavos indiscriminately with smaller sizes; and a base
shelf for quartos and folios, at a proper height from the floor, will
restrict the number of shelves to six in each tier.

In the arrangement of the cases or book-stacks, the most economical
method is to place book-cases of double face, not less than three feet
apart, approached by aisles on either side, so as to afford free passage
for two persons meeting or passing one another. The cases may be about
ten feet