in France and Germany from bones. It is
got as a by-product in the manufacture of animal charcoal. Although
beautiful to look at, it is found when used to be far inferior to
Scottish hide glue."

PART II

CARE OF BOOKS WHEN BOUND

CHAPTER XXI

Injurious Influences to which Books are Subjected

_Gas Fumes._--The investigation of the Society of Arts Committee shows
that--

"Of all the influences to which books are exposed in libraries, gas
fumes--no doubt because of the sulphuric and sulphurous acid which
they contain--are shown to be the most injurious."

The injurious effects of gas fumes on leather have been recognised for
a long time, and gas is being, very generally, given up in libraries
in consequence. If books must be kept where gas is used, they should
not be put high up in the room, and great attention should be paid to
ventilation. It is far better, where possible, to avoid the use of gas
at all in libraries.

_Light._--The committee also report that "light, and especially direct
sunlight and hot air, are shown to possess deleterious influences
which had scarcely been suspected previously, and the importance of
moderate temperature and thorough ventilation of libraries cannot be
too much insisted on."

The action of light on leather has a disintegrating effect, very
plainly seen when books have stood for long periods on shelves placed
at right angles to windows. At Oxford and Cambridge and at the British
Museum Library the same thing was noticed. The leather on that side,
of the backs of books, next to the light, was absolutely rotten,
crumbling to dust at the slightest friction, while at the side away
from the light it was comparatively sound. Vellum bindings were even
more affected than those of leather.

The committee advise that library windows exposed to the direct
sunlight should be glazed with tinted glass.

"Some attempts have been made to determine the effect of light
transmitted through glasses of different colours, and they point to
the fact that blue and violet glass pass light of nearly as
deleterious quality as white glass; while leathers under red, green,
and yellow glasses were almost completely protected. There can be no
doubt that the use of pale yellow or olive-green glass in library
windows exposed to direct sunlight is desirable. A large number of
experiments have be