A soft brush will be found useful if there is much dust.

The whole exterior should also be rubbed with a soft cloth, and then the covers should be opened and the hinges of the binding examined; for mildew WILL assert itself both inside and outside certain books, and that most pertinaciously.

It has unaccountable likes and dislikes.

Some bindings seem positively to invite damp, and mildew will attack these when no other books on the same shelf show any signs of it.

When discovered, carefully wipe it away, and then let the book remain a few days standing open, in the driest and airiest spot you can select.