The medium became more and more detailed, and eventually rivaled photography in its minute variations of tone (see figs. 15 and 16). But printing wood engravings never was a problem again. Not only was wove paper always used in this connection, but it had become much cheaper through the invention of a machine for producing it in lengths. Nicholas Louis Robert, in France, had developed and exhibited such an apparatus in 1797, at the instigation of M. Didot. John Gamble in England, working with Henry and Charles Fourdrinier, engaged a fine mechanic, Bryan Donkin, to build a machine on improved principles. The first comparatively successful one was completed in 1803. It was periodically improved, and wove paper appeared in increasing quantities. Spicer[29] says: "Naturally these improvements and economies in the manufacture of paper were accompanied by a corresponding increase in output. Where, in 1806, a machine was capable of making 6 cwt. in twelve hours, in 1813 it could turn out double that quantity in the same time at one quarter the expense." [29] A. D. Spicer, _The paper trade_, London, 1907, p. 63. [Illustration: Figure 12.--Wood Engraving by W. J. Linton, 1878 (Actual Size). The detail opposite is enlarged four times to show white line-technique.] [Illustration] [Illustration: Figure 13.--"Pintail Duck" by Thomas Bewick (actual size), from _History of British birds_, vol. 2, 1804. The detail opposite is enlarged three times.] At about the same time the all-iron Stanhope press began to be manufactured in quantity, and shortly the new inking roller invented by the indispensable Earl came into use to supplant the old inking balls. Later in the century (there is no need to go into specific detail here) calendered and coated papers were introduced, and wood engraving on these glossy papers became a medium that could reproduce wash drawings, crayon drawings, pencil drawings, and oil paintings so faithfully that all the original textures were apparent.[30] The engraver, concerned entirely with accurate reproduction, became little more than a mechanic who rendered pictures drawn on the blocks by an artist. In time, photographic processes came to be used for transferring pictures to the blocks and eventually, of course, photomechanical halftones replaced the wood engraver altogether. [Illustration: Figure 14.--Title-Page Illustration by Thomas Bewick, from _History of British birds_, vol. 1, 1797. (Actual size.)] [30] The electrotyping process, which came into prominence in 1839 through the experiments of Professor Jacobi in St. Petersburg and Jordan and Spencer in England, had made it possible to produce substitute plates of the highest fidelity. For fine work, these were much superior to stereotyping.