IV. APPLICATION OF PHOTOGENIC DRAWING.--This method of photogenic drawing may be applied to useful purposes, such as the copying of paintings on glass by the light thrown through them on the prepared paper--Imitations of etchings, which may be accomplished by covering a piece of glass with a thick coat of white oil paint; when dry, with the point of a needle, lines or scratches are to be made through the white lead ground, so as to lay the glass bare; then place the glass upon a piece of prepared paper, and expose it to the light. Of course every line will be represented beneath of a black color, and thus an imitation etching will be produced. It is also applicable to the delineation of microscopic objects, architecture, sculpture, landscapes and external nature. A novel application of this art has been recently suggested, which would doubtless prove useful in very many instances. By rendering the wood used for engravings sensitive to light, impressions may be at once made thereon, without the aid of the artist's pencil. The preparation of the wood is simply as follows:--Place its face or smooth side downwards, in a plate containing twenty grains of common salt dissolved in an ounce of water; here let it remain for five minutes, take it out and dry it; then place it again face downwards in another plate containing sixty grains of nitrate of silver to an ounce of water; here let it rest one minute, when taken out and dried in the dark it will be fit for use, and will become, on exposure to the light, of a fine brown color. Should it be required more sensitive, it must be immersed in each solution a second time, for a few seconds only. It will now be very soon effected by a very diffused light. This process may be useful to carvers and wood engravers not only to those who cut the fine objects of artistical design, but still more to those who cut patterns and blocks for lace, muslin, calico-printing, paper hangings, etc., as by this means the errors, expense and time of the draughtsman may be wholly saved, and in a minute or two the most elaborate picture or design, or the most complicated machinery, be delineated with the utmost truth and clearness. CHAP. IX. CALOTYPE AND CHRYSOTYPE. The materials and apparatus necessary for the Calotype process are-- Two or Three Shallow Dishes, for holding distilled water, iodide, potassium, &c.--the same water never being used for two different operations. White Bibulous Paper. Photogenic Camera--Fig. 9. Pressure Frame--Fig 29. Paper, of the very best quality--directions for the choice of which have been already given. A Screen of Yellow Glass. Camels' or Badgers' hair Brushes:--A seperate one being kept for each wash and solution, and which should be thoroughly cleansed immediately after using in distilled water. That used for the gallo-nitrate is soon destroyed, owing to the rapid decomposition of that preparation. A Graduated Measure.