Pictures of the largest size--eight inches by six--are taken with the French achromatic lenses, perfect throughout; the parts within the shade are brought into view, distant objects are perfectly delineated. A common spectacle lens, an inch in diameter, of fourteen inches focal length, adjusted by means of a sliding tube, into one end of a cigar box, answers very well to take small pictures. In one respect, these pictures are equal to those obtained with the achromatics; they are, however inferior in others, and in their general effect. The fine lines and edges of objects are exceedingly sharp and distinct; but the parts within the shade are not copied, and objects very distant from that to which the focus was adjusted, are not accurately delineated. By placing a diaphragm before the lens, with an aperture half an inch in diameter, the sharpness and distinctness of the lines and edges of objects are increased. In using this apparatus, which recommends itself by its cheapness--costing about twenty-five cents--the tube should be pushed in 2/10 or 3/10 inch, after adjusting the lens to the luminous focus, to obtain that of the chemical rays. The exact distance the tube is to be retracted should be determined for each lens by trial.