In a perfectly dry and warm library these spots would probably remain undeveloped, but many endowed as well as private libraries are not in daily use, and are often injured from a false idea that a hard frost and prolonged cold do no injury to a library so long as the weather is dry.  The fact is that books should never be allowed to get really cold, for when a thaw comes and the weather sets in warm, the air, laden with damp, penetrates the inmost recesses, and working its way between the volumes and even between the leaves, deposits upon their cold surface its moisture.  The best preventative of this is a warm atmosphere during the frost, sudden heating when the frost has gone being useless.

Our worst enemies are sometimes our real friends, and perhaps the best way of keeping libraries entirely free from damp is to circulate our enemy in the shape of hot water through pipes laid under the floor.  The facilities now offered for heating such pipes from the outside are so great, the expense comparatively so small, and the direct gain in the expulsion of damp so decided, that where it can be accomplished without much trouble it is well worth the doing.

At the same time no system of heating should be allowed to supersede the open grate, which supplies a ventilation to the room as useful to the health of the books as to the health of the occupier.  A coal fire is objectionable on many grounds.  It is dangerous, dirty and dusty.  On the other hand an asbestos fire, where the lumps are judiciously laid, gives all the warmth and ventilation of a common fire without any of its annoyances; and to any one who loves to be independent of servants, and to know that, however deeply he may sleep over his “copy,” his fire will not fail to keep awake, an asbestos stove is invaluable.

It is a mistake also to imagine that keeping the best bound volumes in a glass doored book-case is a preservative.  The damp air will certainly penetrate, and as the absence of ventilation will assist the formation of mould, the books will be worse off than if they had been placed in open shelves.  If security be desirable, by all means abolish the glass and place ornamental brass wire-work in its stead.  Like the writers of old Cookery Books who stamped special receipts with the testimony of personal experience, I can say “probatum est.”

CHAPTER III.

GAS AND HEAT.

WHAT a valuable servant is Gas, and how dreadfully we should cry out were it to be banished from our homes; and yet no one who loves his books should allow a single jet in his library, unless, indeed he can afford a “sun light,” which is the form in which it is used in some public libraries, where the whole of the fumes are carried at once into the open air.