there is not a hiatus like an empty space which is inclosed within the four sides of a picture. The only exceptions to the necessity for restoration in damaged pictures are those cases in which a fragment of ancient painting is preserved less as a work of art than as an object of antiquarian interest. Then, of course, however mutilated, it must remain in its mutilated condition like all those things which are valuable as materials for antiquarian studies.
Vermin have to be guarded against carefully in the preservation of works of art. Drawings and engravings are generally protected either by portfolios or by glass, which prevent the droppings of flies from spotting them; but I have seen prints spoiled in this way by being carelessly left upon a table for a very short time, when the flies took their opportunity and left their black dots. Their excrement is soluble in water, and can be removed easily from any hard substance while it is fresh, though it hardens and becomes less soluble afterward; but on an engraving it is disastrous, as it sinks into the paper like a stain. It therefore becomes a necessary precaution, especially in summer, to cover a print that is left on a table, or, better still, never to leave prints on tables at all.
The worms that bore into wood are dangerous only to pictures on panels, and, as very few pictures are painted upon wood in these days, this enemy is not so much to be feared. When he attacks an old panel his holes may be stopped with a little marine glue, applied hot; but it is curious how often worms will attack a thin piece of wood without penetrating to the other side. In two specimens before me, small panels three eighths of an inch thick, and about four inches by five, I find that in one case the worms have made twenty-two holes, not one of which has got through to the other side: and in the other case there are twenty-five holes, of which only seven have as yet penetrated.
The only way to keep prints and drawings from the attacks of rats and mice is to have them always in closed cases if they are not framed, and, if the cases are of wood, it is a good precaution to have them covered with thin sheet-iron behind and beneath, while the front panels may be glazed. Tin boxes are a perfect protection against rodents, and so, of course, is glass. Common portfolios are a poor protection, as a rat willingly attacks them, and soon eats his way through to the prints; in fact, common portfolios are in all ways unsafe, being of use only to keep order. The danger from rats and mice is always present, for even in places where they are unknown they may at any time suddenly make their appearance. A rat may find his way into your best protected room. I remember one summer's day—in broad daylight, too—seeing a large rat quietly descending into my study by means of a window-curtain, the window having been left open. He had walked along a little stone ledge that the architect had carried round the house as an ornament, which is a great convenience to rats. When a house is perfectly quiet at night a rat will wander about in the coolest man-
