Page:Popular Science Monthly Volume 45.djvu/331

 made, which takes only a few minutes, the time depending upon the strength of the light and the porosity and translucency of the wood, the print is subjected to the toning process, and, after washing and drying, is ready to become the negative from which the final print is made. In order that the light may pass more readily through the negative it is soaked for a few minutes in kerosene and wiped dry upon the surface. The negative is then placed paper side down upon the plain glass in the printing frame, and upon its face is brought the sensitive side of a fresh sheet of paper, the two sheets being pressed close to each other and evenly against the glass by the clamps, as before stated. In a very brief period a positive print is obtained, which upon removal is toned in the usual way, and becomes a picture the one, for example, furnishing the subject for the engraving in Fig. 2.

What with the brief description of the manner in which solar prints of translucent objects are made, the reader may wish to go



further and consider some of the differences of detail in the various kinds of wood, for one kind of timber differs from another in many ways. Should we, for example, turn to the Report on the Forests of North America, in the last census, no less than four hundred and twelve kinds of timber would be found distributed