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SCIOPTICON MANUAL. 73 flame to get intensity from a single point. A narrow strip of glass sets into this slit as between two lips. The thickness of the flame gives the horizontal diameter of the point of light. Only the front of the lamp is shown at the right of Fig. 24, hut it can be seen how the light from the whole width of the flame reaches the printing- frame through the narrow aperture. At the left, we see how the negative is held over the opening in the frame by four springs; the long spring on the opposite side holds the sensitive plate in the frame. The operator, standing on the opposite side, with the upper corners of a quarter plate, just from the bath, between his thumb and finger, and shading off direct rays with his left hand, places it in its silver bearings j this brings the two films almost in contact. The lamp and frame stand from 16 to 26 inches apart, or so far as to require about two minutes for the print- ing, or the time it takes for a round of the other manipu- lations and changes; so a picture is finished and dropped into grooves in a trough of water as often as one has had time to print. All that is said in the previous article on the wet- plate process, in regard to development, &c., applies here. Any drops of silver bath that may have come in contact with the negative must be washed off before it is put away. Like dry-plate printing, the negative must be of the exact size required for the lantern slide. Some of the advantages of this method are: 1. It can be practiced evenings or in cloudy weather. 2. The light is inexpensive. 3. Plate glass is not a necessity. 6