In 1872 Woodbury patented a method of applying his process to the production of rolls from which to print in the cylinder or rotary press, thus reversing the method patented by Pretsch in 1855, by utilizing the wash-out instead of the swelled gelatine process for the purpose. Neither method, however, was found practicable.

The method of procuring intaglio photo-engravings in grain effect by etching the plate to modulated depth through the exposed gelatine film, which Talbot had devised at the very beginning of his work in 1854 and had patented as the first of his results, was gradually improved in its details, first by Talbot himself and afterwards, during the sixties, by several of his followers. Among these were a number of French workers, notably Dujardin and Rousselon, who, by applying the wash-out gelatine process devised by Poitevin and modified by Swan and Woodbury, obtained, both by electrotype and etching process, intaglio photo-engravings of a quality which left nothing to be desired and which made the Parisian art publishing house of Goupils famous. The method by etching was afterwards, about 1880, simplified by an Austrian worker, Carl Klic, but, through having been brought to its full development in France, it continues to be known everywhere by its French term, photogravure.

Yet another pioneer worker, Georg Scamoni, chief of the photographic section of the Russian Imperial Printing Office at St. Petersburg, added materially to the progress of the Technographic Arts during this period. He worked out, about 1865, a method of photo-intaglio-reproduction by electrotyping on the metallic deposit which forms the image on the developed collodion plate, after first building this up to a sufficient relief by repeated redevelopment and intensification. His line reproductions by this process were used extensively for official documents and show a remarkable degree of delicacy of line and stipple.

From this time on the field of the Techno-graphic Arts rapidly widened out and the number of workers in it grew apace. I became one of these in Milwaukee in 1869 as an experimenter with swelled gelatine along the lines marked out by Pretsch, at the same time finding occasion to learn the methods and also the troubles of the collotype process. After a long interruption I began again in Baltimore in 1873, and in the following year

obtained the facilities of David Bachrach's photographic gallery and also his coöperation in the working out of a new photoelectrotype process which, to distinguish it from its predecessors, we called the Levytype. Its essential features consisted in swelling the exposed chrome gelatine film in solution of silver nitrate, making this electrolytic by changing it into a sulphuret and electrotyping the mould thus produced. For this process we obtained a patent which was published in January, 1875.

In May of the same year a photo-electrotype process based on Poitevin's method of washing out the unexposed gelatine film instead of swelling it was patented by William Mumler, of Boston. His method was an adaptation of that of Fontaine, worked out in Paris in 1862, which consisted in washing out the unexposed portion of a thick chrome gelatine film and electrotyping the dried gelatine relief. This method found considerable application both in Europe and this country until superseded by the zinc etching process.

After working the swelled gelatine process commercially for about a year I came gradually to taking wax casts from the gelatine film and electrotype moulds from these, and from this it was but a step to using the wax casts for making plaster moulds in which to produce the relief plates in the form of stereotypes. My next step was taken in 1877 in the form of a removal to Philadelphia. Here, in 1880, I took up the zinc etching process which had long been practised in Europe, notably by Gillot in Paris, and which was then being used for the production of the United States Patent Office Gazette. In this process a photo-lithographic print was transferred to the surface of the polished zinc plate, the transfer strengthened with asphaltum powder melted into the ink and the plate then etched with nitric acid, leaving the surface protected by the inked design standing in relief. As the etching proceeded the vertical sides of the standing lines required to be protected against the action of the acid, and this was effected by applying additional ink and powder to the surface of the plate and then heating it to make the ink run down over the sides of the exposed lines. This was repeated usually seven or eight times until the etching had reached a sufficient depth for the requirements of the printing press. My experience with this method soon led me to the expedient of sensitizing the surface of the zinc instead of the paper

and producing the design on the plate directly by exposure instead of indirectly by transfer. I next came to replace the inking-up and melting-down method of protecting the exposed lines of the etching by covering them instead with a shield of resinous powder brushed against the projecting lines and melted into place. This was done four times at right angles across the plate and proved to be sufficiently effective to permit the etching process to be completed in three or four stages instead of double that number. From here this four-way method of powdering became gradually disseminated through the craft and is known in Europe as the American method.

It was about this time, 1882, that the method of producing photo-engravings in halftone by means of an intervening screen of fine lines, first practised by Talbot in 1852 and gradually improved by a number of later workers, was brought to the point of successful application by Georg Meissenbach in Munich. Two other commercially applicable methods of producing halftone photo-engravings had previously been worked out, one by our subsequent fellow-member, Frederick E. Ives, in this city, and the other by Charles G. Petit in Paris. The former had begun in 1878 to obtain his results by inking up the surface of a modulated relief, obtained by the gelatine wash-out method from a transparent positive, and pressing this down on a sheet of paper the surface of which presented lines or stipples embossed in relief. The lights of the picture being low in the gelatine relief and the shadows high, the embossed paper would be pressed out more or less according to the gradations of light and shade of the subject as represented by the modulated relief of the gelatine film. The process was later modified by inking the surface of the embossed lines or stipples instead of the gelatine relief and bringing the inked surface in contact with a plaster cast from the gelatine. In either case the resulting black-and-white halftone effect was photographed to obtain a negative, from which in turn the final printing plate was produced in the form of a photo-electro or stereotype. Petit's process was similar in all respects, except that he inked the surface of the plaster cast and then cut across it in a ruling machine with a V-shaped tool. As this cut deepest into the raised portion of the relief representing the lights of the picture and left the depression more or less untouched, there was produced an effect of halftone which was