94 ANNUAL OF SCIENTIFIC DISCOVERY. 



In 1707 Linnreus alludes to impressions taken by Hessel, from nature, 

 who, at a later period, carried this art out to a considerable extent. The 

 leaf or vegetable subject was prepared by being dabbed with printer's ink or 

 lamp-black, after which it was placed between two sheets of paper, and sub- 

 jected to flat pressure. Coloring the impressions by hand was introduced 

 about this time, but not successfully. 



Hitherto all the modes of producing impressions of plants have been sim- 

 ilar, all involving a preparation of the botanical subject with a black pig- 

 ment, and the application of pressure to procure the transfer. No attempt 

 was made to multiply the impressions produced, a new vegetable subject be- 

 ing used for every impression or nearly so. 



In 1833 nature printing again appeared, but it amounted to a new dis- 

 covery. 



The process was the discovery of Peter Kyhl, a Danish goldsmith. The 

 vegetable subject, after being thoroughly dried, was placed between a plate 

 of polished steel and a thoroughly heated lead-plate, which were united and 

 passed between steel rollers, by which operation the plant became pressed 

 into the lead, thus producing in this soft metal a beautiful concave image of 

 itself. 



The next step was the proposal of Professor Leydolt, in 1849, viz., that 

 of printing from agates in such a manner as to represent themselves in a 

 truthful manner. The agate is exposed to the action of fluoric acid, the re- 

 sult of which is; certain of the concentric scales are decomposed, while others 

 remain unaltered ; after this the surface is well washed with dilute hydro- 

 chloric acid and dried,, then carefully blackened with printer's ink. A piece 

 of paper being placed upon the prepared stone and rubbed with a burnisher, 

 an impression was produced, the black parts being represented white, and the 

 white black. This is now overcome by the surfaces being reversed : that is, 

 the concave surface made convex, and the convex concave, which is effected 

 by casting. 



Dr. Ferguson Branson, in 1851, suggested the application of the electro- 

 type, which has since proved itself to be an essential feature in this art. In 

 1852, he again made experiments. The mode he adopted was that of taking 

 impressions upon Britannia metal, with a view of transfering them to stone, 

 and after printing in neutral tint, to color such impressions by hand. This, 

 however, failed to produce any practical results. 



The next step was taken in the imperial printing office of Vienna, in 1851, 

 or early in 1852. The first experiment made there appears to have been 

 casting with gutta-percha, as Dr. Branson had done, but as this material did 

 not altogether answer, Andrew AVorring proposed the substitution of soft 

 lead, which he used as Kyhl had forrniy clone ; the specimens operated upon 

 being lace. Professor Haidinger proposed the application of the process to 

 plants, which suggestion Worring gladly availed himself of. After he had 

 prepared the moulds, in the manner just described, he, by the agency of the 

 electrotype, produced plates prepared for the printing-press. This process 

 was at once applied to practical purposes, and several botanical works have 

 already been illustrated by his agency. This process Avas first patented in 



