Nature-printing,also called Autotypography,is an invention introduced from the Imperial printing-office in Vienna, by the late Mr. Henry Bradbury. The merit of the discovery has been a matter of contest into which we shall not enter, hut we may remark that M. WORRING (in Btoo. Dtv.), to whom we have attributed much of it, has disclaimed all beyond carrying into effect the suggestions of Councillor Auer, the director of the Imperial printing-office. The invention successfully pretends to give an exact reproduction of natural objects, such as plants, the grain of wood, &e. ; and of other flat substances, such as lace, &c., in a form which enables a large number of impressions to be printed, and in their natural colours. The transference of the forms of plants to paper had been effected even centuries since, either by staining the plants, or by simple pressure. In this manner, however, the object, after taking a few impressions, was rendered useless. At Vienna the art was rendered more perfect by taking an impression on polished lead, from which impressions could be printed, though still in only a very limited number. Softened copper-plates were then adopted, which were found equally capable of receiving the impression, to its minutest markings, of the substance pressed on it. The object is arranged on the plate in the desired form, and is then subjected to an enormous pressure for a sufficient time, when it is found that the object has left its form deeply impressed upon the plate. This piste is subsequently hardened, and is fitted to furnish a large number of impressions. The plates are coloured, or inked as it is termed, with the proper colours of the plant, which is easily done, as the face of the plate is wiped after each colour has been laid on ; the paper is laid upon the plate and passed through a press formed of two cylinders pressing against each other, of which one is covered with thick blanketing. and with a regulated pressure, the impression is produced in a low relief. In Vienna, several works of a magnificent character have been produced. ' In land there have been three, The Ferns of Great Britain ;"Britisl Sea Weeds;' and ' Trees of Great Britain ; ' all of which possess a high degree of excellence as works of art, and are of course of unexcep tionable correctness.
Electro-printing.—The processes of the " Electro Printing-Block Company" (patented by Mr. H. G. Collins) supply the means of repro ducing drawings, engravings, &c., without the aid of copyist or engraver, net only of the name size as the original, but enlarged or reduced with strict accuracy to any extent that may be desired. Thus, from a wood cut or steel engraving, say of 6 inches by 4, a working plate or block can be produced that will yield impressions 12 inches by 8, or 3 inches by 2, or of any other required proportion. We will briefly describe the beautifully simple means by which this is effected, and then indicate a few of its actual or probable applications.
The whole, in fact, depends on the capacity of india-rubber for extension in any direction, and its property of returning to its original size when the tension is removed. Let us suppose that it is desired to obtain an enlarged copy of an engraving. The surface of a sheet of galvanised india-rubber, the size of the print, is covered with a film of an elastic composition, and upon this film, when dry, an impression of the print is taken by means of transfer ink. The sheet so printed upon is then placed in a rectangular steel frame, hooks from the sides of the frame passing through holes pierced at equal intervals in the edges of the india-rubber. By a simple but ingenious double screw action, two opposite sides of the frame are now gradually drawn apart, till it is seen, by a scale engraved on the sides, that the india-rubber sheet is sufficiently extended. The same is done with the other two sides ; and the whole having been carefully examined to see that the enlargement, is uniform, the frame is fixed, in order that the strained sheet may not be in any way disturbed during the next operation. The impression
thus enlarged on the india-rubber is now transferred by the ordinary lithographic transfer process to a lithographic stone, or zinc plate, which, after the usual treatment LLITHOORAPHY], yields impressions exactly like any other prepared lithographic stone.
For a reduced copy, the only difference in the process is, that an I rubber sheet of the desired size is strained to the dimensions of print to be copied, before the impression is placed upon it, and t en allowed to contract to its original Aire, when the impression is transferred to the stone. It ought perhaps to be mentioned that first of all the india-rubber sheet has printed upon it thin linca, which divide its whole surface into squares of a quarter of en inch each, thus, affording, by means of the T square and compasses, an easy means of detecting the slightest inequality of extension in any part during the process of enlarging, whilst the frame is so constructed as to permit any deviation to be at once remedied.
For obtaining blocks for tlirfa re-pristing, an tulditional protese is required. After the enlarged (or reduced) impression is transferred to the lithographic stone or zinc plate, the surface of the stone or zinc is exposed to the action of an acid, which eats away all the parts not pro tected by the ink. The print is thus left in raised lines corresponding to those of an engraved wood-block. A matrix is taken in some suitable material, and upon this a cast, corresponding to the original wood block, or a stereotype from it, is formed by the ordinary method of electrotype deposit. [ELEcnto-Iffinsttunce.] The processes we have described suffice for all the usual purposes of lithographic printing, and printing by the ordinary type-preas. To both there are limitations within which only success can be at present assured. Mezzotint, or finely stippled plates, for instance, cannot be successfully reproduced ; but ordinary steel plates, wood-cuts, music, maps, and plane, can be enlarged or reduced with minute accuracy, and printed as lithographs with perfect certainty. The surface-block is somewhat less certain ; but very beautiful results have been obtained, and the manipulative difficulties appear in a fair way of being overcome.
The further applications of the process seem almost illimitable. For surveying and engineering purposes, for example, a sheet of the Ordnance map could be taken, and in a few hours a copy be produced large enough to admit of the insertion of any amount of local detail. For the potter 'a use, from a single small drawing or print of a pattern, copies to any extent may be produced, to suit the various sizes of all the articles of a tea- or dinner-service ; and if the original pattern be circular, it may be altered to an oval for dishes, &c. Its application to various other branches of ornamental art and manufacture, where variations of the size or form of designs are required, is obvious: whilst in fine art, the small pen or pencil sketch of an artist may at once, by mere mechanical means, be reproduced as a good-sized litho graph ; the original study of a painter, if he choose so to work, bo enlarged ready to his hand on his canvas, preparatory to.painting ; the diagram of the man of science speedily be reproduced of a size suitable for the lecture-room. Another application which the process is said to be already quite capable of carrying into practice is, that of reproducing impressions (of course of any size required) of books or engravings, even though a couple of centuries may have elapsed since they were printed. And any of these applications of the method is obtainable at a comparatively small cost.