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 been made on the tinted 'cathedral' glasses of Messrs. Pilkington Bros., Limited, with the result that Nos. 812 and 712 afforded almost complete protection during two months' exposure to sunlight, while Nos. 704 and 804 may be recommended where only very pale shades are permissible. The glasses employed were subjected to careful spectroscopic examination, and to colour-measurement by the tintometer, but neither were found to give precise indications as to the protective power of the glasses, which is no doubt due to the absorption of the violet, and especially of the invisible ultra-violet rays. An easy method of comparing glasses is to expose under them to sunlight the ordinary sensitised albumenised photographic paper. Those glasses under which this is least darkened are also most protective to leather."
_Tobacco._--Smoking was found to be injurious, and it is certainly a mistake to allow it in libraries.
"The effect of ammonia vapour, and tobacco fumes, of which ammonia is one of the active ingredients, was also examined. The effect of ammonia fumes was very marked, darkening every description of leather, and it is known that in extreme cases it causes a rapid form of decay. Tobacco smoke had a very similar darkening and deleterious effect (least marked in the case of sumach tanned leathers), and there can be no doubt that the deterioration of bindings in a library where smoking was permitted and the rooms much used, must have been partly due to this cause."
_Damp._--Books kept in damp places will develop mildew, and both leather and paper will be ruined.
Where possible, naturally dry rooms should be used for libraries, and if not naturally dry, every means possible should be taken to render them so. It will sometimes be found that the only way to keep the walls of an old house dry is to put in a proper dampcourse. There are various other methods employed, such as lining the walls with thin lead, or painting them inside and out with some waterproofing preparation: but as long as a wall remains in itself damp, it is doubtful if any of these things will permanently keep the damp from penetrating.