The pictures we have examined thus far in this collection have been reproductions from Rembrandt's paintings. You will see at once that the picture of the Rat Killer is of another kind. The figures and objects are indicated by lines instead of by masses of color. You would call it a drawing, and it is in fact a drawing of one kind, but properly speaking, an etching. An etching is a drawing made on copper by means of a needle. The etcher first covers the surface of the metal with a layer of some waxy substance and draws his picture through this coating, or "etching ground," as it is called. Next he immerses the copper plate in an acid bath which "bites," or grooves, the metal along the lines he has drawn without affecting the parts protected by the etching ground. The plate thus has a picture cut into its surface, and impressions of this picture may be taken by filling the lines with ink and pressing wet paper to the surface of the plate. You will notice that the difference between the work of an engraver and that of an etcher is that the former cuts the lines in his plate with engraving tools, while the latter only draws his picture on the plate and the acid cuts the lines. The word etching is derived from the Dutch _etzen_, and the most famous etchers in the world have been among Dutch and German artists. Rembrandt is easily first of these, and we should have but a limited idea of his work if we did not examine some of his pictures of this kind. Impressions made directly from the original plates, over two centuries ago, are, of course, very rare and valuable, and are carefully preserved in the great libraries and museums of the world. There is a collection in the Museum of Fine Arts, Boston, where this etching of the Rat Killer may be seen. The Rat Killer is one of many subjects from the scenes of common life which surrounded the artist. In smaller towns and villages, then as well as now, there were no large shops where goods were to be bought. Instead, all sorts of peddlers and traveling mechanics went from house to house--the knife grinder, the ragman, the fiddler, and many others. This picture of the Rat Killer suggests a very odd occupation. The pest of rats is, of course, much greater in old than in new countries. In Europe, and perhaps particularly in the northern countries of Holland and Germany, the old towns and villages have long been infested with these troublesome creatures. [Illustration: THE RAT KILLER _Museum of Fine Arts, Boston_] There are some curious legends about them. One relates how a certain Bishop Hatto, as a judgment for his sins, was attacked by an army of rats which swam across the Rhine and invaded him in his island tower, where they made short work of their victim.[4] Another tells how a town called Hamelin was overrun with rats until a magic piper appeared who so charmed them with his enchanted music that they gathered about him and followed his leading till they came to the river and were drowned.[5]