"While England does not excel in the manufacture, it is a recognised fact that Scottish glue ... ranks in the front of the glues of all countries. A light-coloured glue is not necessarily good, nor a dark-coloured glue necessarily bad. A bright, clear, claret colour is the natural colour of hide glue, which is the best and most economical.
"Light-coloured glues (as distinguished from gelatine) are made either from bones or sheepskins. The glue yielded by these materials cannot compare with the strength of that yielded by hides.
"A great quantity is now made 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."
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.