to reproduce freehand line drawings. This was, in many ways an unnatural application, since engravers had to cut away almost all the surface of the block to produce the printable lines of the artist's drawing. Nonetheless, it became the most common use of wood engraving. Examples include the cartoons of Punch magazine, the pictures in the Illustrated London News and Sir John Tenniel's illustrations to Lewis Carroll's works, the latter engraved by the firm of Dalziel Brothers. In the United States, wood-engraved publications also began to take hold, such as Harper's Weekly. Frank Leslie, a British-born engraver who had headed the engraving department of the Illustrated London News, immigrated to the United States in 1848, where he developed a means to divide the labor for making wood engravings. A single design was divided into a grid, and each engraver worked on a square. The blocks were then assembled into a single image. This process formed the basis for his Frank Leslie's Illustrated Newspaper, which competed with Harper's in illustrating scenes from the American Civil War. New techniques and technologies By the mid-19th century, electrotyping was developed, which could reproduce a wood engraving on metal. By this method, a single wood-engraving could be mass-produced for sale to printshops, and the original retained without wear.Until 1860, artists working for engraving had to paint or draw directly on the surface of the woodblock and the original artwork was actually destroyed by the engraver. In 1860, however, the engraver Thomas Bolton invented a process for transferring a photograph onto the block. At about the same time, French engravers developed a modified technique (partly a return to that of Bewick) in which cross-hatching (one set of parallel lines crossing another at an angle) was almost eliminated. Instead, all tonal gradations were rendered by white lines of varying thickness and closeness, sometimes broken into dots for the darkest areas. This technique appears in wood-engravings after Gustave Doré. Towards the end of the 19th century, a combination of Bolton's 'photo on wood' process and the increased technical virtuosity initiated by the French school gave wood engraving a new application as a means of reproducing drawings in water-colour wash (as opposed to line drawings) and actual photographs. This is exemplified in illustrations in The Strand Magazine during the 1890s. With the new century, improvements in the half-tone process rendered this kind of reproductive engraving obsolete. In a less