uld mildew make its appearance, the books should be taken out,
dried and aired, and the bookshelves thoroughly cleaned. The cause of
the damp should be sought for, and measures taken to remedy it.
Library windows should not be left open at night, nor during damp
weather, but in warm fine weather the more ventilation there is, the
better.

_Heat._--While damp is very injurious to books on account of the
development of mildew, unduly hot dry air is almost as bad, causing
leather to dry up and lose its flexibility. On this point the Chairman
of the Society of Arts Committee says:--

"Rooms in which books are kept should not be subject to extremes,
whether of heat or cold, of moisture or dryness. It may be said that
the better adapted a room is for human occupation, the better for the
books it contains. Damp is, of course, most mischievous, but
over-dryness induced by heated air, especially when the pipes are in
close proximity to the bookcases, is also very injurious."

_Dust._--Books should be taken from the shelves at least once a year,
dusted and aired, and the bindings rubbed with a preservative.

To dust a book, it should be removed from the shelf, and without being
opened, turned upside down and flicked with a feather duster. If a
book with the dust on the top is held loosely in the hand, and dusted
right way up, dust may fall between the leaves. Dusting should be done
in warm, dry weather; and afterwards, the books may be stood on the
table slightly open, to air, with their leaves loose. Before being
returned to the shelves, the bindings should be lightly rubbed with
some preservative preparation (see chap. XXII). Any bindings that are
broken, or any leaves that are loose should be noted, and the books
put on one side to be sent to the binder. It would be best when the
library is large enough to warrant it, to employ a working bookbinder
to do this work; such a man would be useful in many ways. He could
stick on labels, repair bindings, and do many other odd jobs to keep
the books in good repair.

A bookbinder could be kept fully employed, binding and repairing the
books of a comparatively small library under the direction of the
librarian.

BOOKWORMS

The insects known as bookworms are the larvae of several sorts of
beetles, most commonly perhaps of _Antobium domesticum_ and _Niptus
hololencus_. They are not in any way peculiar to books and will infest
the wood of bookshelv