The focussing is conducted in the usual way and the cap replaced on the lens; the focussing glass is now removed and the camera back fitted into the same aperture, with the sliding flap next the lens. The sliding flap is pulled up to its fullest extent, placing the hand on the camera back to prevent it rising out of the camera with this action. The cap of the lens is then removed, so that the light may be admitted into the camera, and to fall on the sensitive surface of the plate. After the necessary time of exposure has taken place, the cap is replaced on the lens, the sliding flap is pushed down, and the camera back withdrawn from the camera; the plate can then be taken into the operating room to be developed, or this operation may be deferred for days or even a week, or more if convenient. The time of exposure in the camera varies according to the intensity of the light and the aperture and focal length of the lens; therefore, to give the exact time of exposure would be impossible, still it may assist the amateur if I give the time required in summer with full sunshine, and merely state that this time may be increased to double in winter or dull weather. In the ordinary sunshine of a summer's day the time of exposure will be: 30 seconds with a lens of 4-inch focus and 1/2-inch stop. 21 seconds with a lens of 4-inch focus and 5/8-inch stop. 5 seconds with a lens of 4-inch focus and 1-1/4 inch aperture with no stop. 1-1/2 minute with a lens of 6-inch focus and 1/2-inch stop. 4-1/2 seconds with a lens of 6-inch focus and 2-1/4-inch aperture with no stop. 2 minutes with a lens of 8-inch focus and 1/2-inch stop. 1-1/4 minute with a lens of 8-inch focus and 5/8-inch stop. 3-1/4 minutes with a lens of 10-inch focus and 1/2-inch stop. 2 minutes with a lens of 10-inch focus and 5/8-inch stop. 5 seconds with a lens of 10-inch focus, 3-1/4-inch aperture, with no stop. 6-1/4 minutes with a lens of 14-inch focus and 1/2-inch stop. 4 minutes with a lens of 14-inch focus and 5/8-inch stop. 2-1/4 minutes with a lens of 14-inch focus and 3/4-inch stop. 8-1/4 minutes with a lens of 16-inch focus and 1/2-inch stop. 5-1/4 minutes with a lens of 16-inch focus and 5/8-inch stop. 2-1/4 minutes with a lens of 16-inch focus and 3/4-inch stop. _Developing the Image._