Actually, white-line engraving for relief printing dates from the 15th century. The most conspicuous early examples are the so-called "dotted prints" or "gravures en manière criblée," in which the designs were brought out by dots punched in the plates, and by occasional engraved lines (see fig. 3). Until Koehler's[10] study made this fact plain, 19th-century critics could hardly believe that these were merely white-line metal relief prints, inked on the surface like woodcuts. But a number of other examples of the same period exist which were also made directly on copper or type metal--the method, although rudimentary, being similar in intent to 19th-century wood engraving. One of these examples (fig. 4), in the collection of the U. S. National Museum, is typical. This was not simply an ordinary line engraving printed in relief rather than in the usual way; the management of the lights shows that it was planned as a white-line engraving. The reason for this treatment, obviously, was to permit the picture and the type to be printed in one operation. The well-known wood engravings of soldiers with standards, executed by Urs Graf in the early 1500's, are probably the only white-line prints in this medium by an accomplished artist until the 18th century. But these are mainly in outline, with little attempt to achieve tones. No advantage was gained by having the lines white rather than black other than an engaging roughness in spots: the prints were simply whimsical excursions by an inventive artist. [10] Sylvester R. Koehler, "White-line engraving for relief-printing in the fifteenth and sixteenth centuries," in _Annual report of the ... Smithsonian Institution ... for the year ending June 30, 1890, report of the U. S. National Museum_, Washington, 1892, pp. 385-389. [Illustration: Figure 4.--White-Line Engraving on Metal for Relief Printing, "The Franciscan, Pelbart of Temesvar, Studying in a Garden," from "_Pomerium quadragesimale, fratris Pelbarti ordinis sancti Francisci_," Augsburg, 1502.] Relief engraving on type metal and end-grain wood really got under way as a consistent process in England at the beginning of the 18th century. Chatto[11] gives this date as conjecture, without actual evidence, but a first-hand account can be found in the rare and little-known book, published in 1752, in which the combination of anonymous authorship and a misleading title obscured the fact that it is a digest of John Baptist Jackson's manuscript journal. This eminent woodcutter, who was born about 1700 and worked in England during the early years of the century, must be considered an important and reliable witness. The unknown editor paraphrases Jackson on the subject of engraving for relief purposes:[12]