Other engravers of eminence that flourished during this period are, in line, the Bromleys, John Landseer and his sons, Charles Heath, William B. Cooke and his brother George,[65] John Burnet (celebrated as painter, engraver, and author), Richard Golding, and John Scott; in stipple, William Bond, Thomas Woolnoth, and James Hopwood; in mezzotint, Henry Dawe, William Say, Henry Meyer, George Clint, and his pupil Thomas Lupton, who, for his introduction of soft steel instead of copper as the medium for mezzotint engraving, received in 1822 the gold Isis medal from the Society of Arts. The method of stipple was meanwhile slowly dying out, but, as often happens when some particular art seems about to expire, this was the very time when the capabilities of the style were shown in the highest perfection. William Walker, born in Musselburgh in the year 1791, served an apprenticeship to three engravers, Mitchell, Stewart, and Thomas Woolnoth, and choosing stipple as his method of interpretation, in his portraits of Sir Walter Scott, Raeburn, and the Earl of Hopetoun, justified his choice by executing the finest works that were ever accomplished in the style. He astonished the mezzotinters of the period--who told him that, do what he could, he would never make stipple equal mezzotint in colour[66]--by the amount of force, colour, and effect which he was able to give to these plates. It is needless to say that such work as this could only be accomplished at the expense of intense energy and persevering labour, qualities which were the essential characteristics of the Scotch engraver. Later on, when settled in London, and more particularly after the introduction of steel in place of copper, Walker chiefly practised mezzotint, in which, however, he made use of his previous experience, etching his subject first in stipple before laying the mezzotint ground. His plate of Burns, engraved in mezzotint by himself and Mr. Cousins, owes a great part of its renown to Walker's power of rendering likeness; in regard to this, the painter Alexander Nasmyth remarked, on seeing the finished print, "that all he could say was that it seemed to him a better likeness of the poet than his own picture." This particular quality of fidelity in likeness Walker carried out in all his after historical works; for this purpose no trouble was too much, no labour too severe; the engraving of the "Distinguished Men of Science assembled at the Royal Institution in 1807-8," which occupied a period of six years of unceasing research and labour, is a striking instance. This was practically his last plate. He died at the age of seventy-six, in the year 1867, at his house in Margaret Street, Cavendish Square, and was buried at Brompton Cemetery.