"The slowness may depend in part on the proportions of bromide and nitrate not being correctly balanced, especially as the ordinary, not the anhydrous, bromide was used, and on the quantities being too small for the proportion of gelatine. Whether the plates would be more sensitive if used when only surface dry is a question of experiment; also, whether other bromides than the one tried may not prove more advantageous in the presence of the neutral salt resulting from the decomposition, or the omission or decrease of the quantity of _aqua regia_. Very probably also the development by gallic acid and acetate of lead developer may furnish better results than the plain pyro. "As there will be no chance of my being able to continue these experiments, they are placed in their crude state before the readers of the Journal, and may eventually receive correction and improvement under abler hands. So far as can be judged, the process seems quite worth more carefully conducted experiments, and, if found advantageous, adds another handle to the photographer's wheel. R. L. Maddox, M.D." After perusing the above, it will be evident to any one that Dr. Maddox very nearly arrived at perfection in his early experiments. The slowness that he complains of was caused entirely by not washing the emulsion to discharge the excess of bromide, and the want of density was due to the absence of a restrainer and ammonia in the developer. He only made positive prints from negatives; but the same emulsion, had it been washed, would have made negatives in the camera in much less time. Thus, it will be seen, that Dr. Maddox, like the Rev. J. B. Reade, threw the ball, and others caught it; for the gelatine process, as given by Dr. Maddox, is only modified, not altered, by the numerous dry plate and gelatino-bromide paper manufacturers of to-day. Meanwhile collodion held the field, and many practical men thought it would never be superseded. In this year Sir John Herschel died at a ripe old age, seventy-nine. Photographers should revere his memory, for it was he who made photography practical by publishing his observation that hyposulphite of soda possessed the power of dissolving chloride and other salts of silver. [Illustration: FOURTH PERIOD. GELATINE. Dr. R. L. MADDOX. _From Photograph by J. Thomson._ GELATINO-BROMIDE EMULSION 1871. R. KENNETT. _From Photograph by J. Werge, 1887._ GELATINO-BROMIDE PELLICLE 1873 DRY-PLATES 1874] FOURTH PERIOD. GELATINE SUCCESSFUL.