The development of trichromatic color photography appears to have superseded experiment along the older lines, by which it was sought to obtain photographs in na tural colors in the ca.mera direct, and this fact is due largely to the work and writings of Mr. Frederic E. Ives, who must also be credited with the attain ment of the most perfect results by means of his Krom skop system, in which a "color record" is first made in a special camera, and then viewed in an optical in strument which is

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... ed like an ordinary stereoscope. In view of the fact that the Kromskop system has now been reduced to a remarkably simple and practi cal basis, and that it yields reproductions which are astonil>hingly beautiful and realil>tic, we feel sUI'e that our readers will be interested in a somewhat detailed explanation and description of the method and the special apparatus devised for carrying it out. As long ago as in 1881, Mr. Ives made trichromatic color prints from half-tone process blocks in the pril,t ing press, but it was not until 1888 that he announced the new principle which is the basis of his perfected methods, and by the application of which he then tirst demonstrated the possibility of accurate color repro duction by an automatic process. This principle, very uriefly stated, is that of making the three images of the color record by the action of mixtures of spectrum rays in accordance with Maxwell's color curves, and then optically combining the three images with pure spectrum colors, red, green , and blue, or by superposed prints in the complimentary colors, cyan blue, crimson, and canary yellow. The optical synthesis has always been Mr. Ives' favorite method, and the application of his new principle to this method involved an important difference in the character of the color sereens eill . . ployed in making the photographs and in viewing them, whereas, all other experimenters had employed the same color screens for both purposes-a fatal defect, according to this inventor. The first demonstration of the method was by means of triple lantern projection; but, with a view to obtain the results by the simplest and most reliable means, aud to render them readily available to everybody, he has succeeded in designing an automatic camera that is an exposure camera for making the negatives, and a viewing device to show the perfect reproduction as readily as stereog'rallls are seen in the stereoscope. Many years before, Louis Ducos Du Hauron, in FI'ance, had endeavored to do the same thing, but he failed to recognize the djstinction which must be made between the taking and viewing color screens, and his viewing device was so crude and imperfect that there is no record of its ever having been exhibited in operation. Undoubtedly the first successful viewing device was Mr. Ives' "Helio-chromoscope," which attracted consider able attention when it was first shown at the Royal Society and at the Royal Institution, in London, in 1892. This device, however, proved too complicated and delicate in its adjustments to meet commercia.l requirements, and the evolution toward greater simplicity and practicability which has since gone on is a most interesting one. The present view ing device is called the" Kromskop," and the abbre, viation of mechanical and optical complications is even