34 THE PHOTOGRAPHIC NEWS. [JANUARY 16, 1885. one of mounting, without which the high gloss got by stripping from the glass will be ruined. The surface of the piint, if it be allowed to dry in the ordinary way, is far from a good one, and the image has a most unpleasant “ sunk-in ” appearance. A yet more serious drawback the process has as yet shown in our hands. We have found it very difficult to get perfectly pure whites, particularly in the case of vig nettes. It is but fair to say that this defect may be due not to the process, but to our working of it ; still we may mention that in the samples of the prints by the process sent out by at least one firm producing the paper, we have Been several prints with distinctly degraded whites. And now for the probable cases in which the application of the process may be useful. In the first place, of course we have the case in which one or more proofs are required in a hurry ; here the new paper will be invaluable, as the working of it does not depend on day light. Then, again, when a photographer requires to issue a large number of prints in a very short space of time, the paper will be most convenient. The rate of production may perhaps not be so rapid as by the Woodbury type process. We should not be surprised if the amateur should be the greatest user of the new paper. Printing is generally his greatest difficulty. He is usually employed in business during the day, when printing on albumenized paper could be carried on. When he has a holiday, he likes to employ it in taking negatives. To him the possibility of making prints of an evening will be the greatest conceivable boon. He will be able to work by lamp or gas-light in winter. We do not in this place quote any of the formu’ pre viously given in the News, as thoroughly practical direc tions for making the development paper arc to be found in Mr. Wellington’s article on page 36, and these directions embody the latest experiences of an exceptionally skilled and successful worker. EXPERIMENTS WITH VIDAL’S COLOUR SENSITOMETER. M. Vidal, in his letter which appears in our issue of last week (p. 21), describes a colour sensitometer made on the same lines as the instrument of Warnerke, but with a series Viole Indigo Blue Gr een Yellow Orange Bed tsocIONLATIC PLATE OF CLAYTON AXDZrAIL.FER. SENSITOMIETER OF LEON VIDAL. ISOCHROXCATIC PLATH. NONOKTOTEX's PLATE. of three grades of density in each of the seven colours of the spectrum. The idea is an excellent one, and by means the sensitiveness of plates for the variously coloured rays may be tested without resorting to delicate spectium experiments. M. Vidal has been good enough to send us his results,
