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100 THE BOOK OF THE LANTERN. the ground side up, the camera lucida may be used with this as well as with drawing-board, if a piece of white paper be placed beneath it, and the object drawn in the usual way. For outlining and delicate shading I employ H H H H and H H H pencils; for deep shadows I use H B. By a very delicate employment of the pencil, shadows softer than can be secured by lithography may be made. The camera lucida, of course, is not necessary ; we may draw with the eye and hand alone. If it be necessary to put on colour it may be done cleanly and carefully over the shading ; thus one layer of colour suffices. Now of course, although we have a perfect drawing of the object, with all the detail accurately given, it is not a transparency. But we can easily make it one. Thin some good pale Canada balsam with benzine to about the consistence of cream; and simply float it over the ground surface of your glass, pour off till the drop comes very sluggishly. Then reverse the glass so that the corner from which the balsam was flowing off be placed upward. Let the return flow reach about the middle, then reverse it again, and move it in several directions to get the balsam level. This may be done with very little practice so that the surface shall be undistinguishable from glass. We have now a perfect transparency. All that is required is twenty -four hours for hardening (keeping the glass level) and then another square of glass fastened on to it by strips of paper at the edges, with small pieces of card at the corners to prevent contact, and it makes an admirable lantern transparency. "For obtaining very fine points to my very hard leads, after cutting them very long and even ? and grinding them on