Diagram.
To these somewhat tentative drawings he afterwards added to the series a diagram, six feet high, of the famous mad dog from one of his Picture Books, and another of the figure of a child running, reproduced above.
The discovery of a process by which a drawing on paper in line, could be photographed and brought into relief, like a wood-block for printing at the type press, was not perfected in England until 1875, and did not come into general use until 1876; had it come a year or two earlier it would have had an important influence upon Caldecott's work.
Diagram.
Without going too far into technicalities, it may be interesting to illustrators to mention here that all Caldecott's best drawings in his Picture Books, John Gilpin, The House that Jack Built, &c.; in the Graphic newspaper, and in Washington Irving's Old Christmas, &c., were photographed on to wood-blocks and have passed through the hands of the engraver.
The system of photographic engraving (by which the drawings are reproduced on pp. 124 and 125) bids fair to supersede wood-engraving for rapid journalistic purposes. It naturally attracted Caldecott in the first instance; but with increased knowledge and perception of "values," and of the quality to be obtained in a good wood-engraving above any mechanical reproduction in relief, Caldecott was glad to avail himself of the help of the engraver. He drew with greater freedom, as he expressed it, preferring, as so many illustrators do, to put in tints with a brush, to be rendered in line by skilful engravers. But at the same time he delighted in shewing the power of line in drawing, studying "the art of leaving out as a science"; doing nothing hastily but thinking long and seriously before putting pen to paper, remembering, as he always said, "the fewer the lines, the less error committed."