even tone, not having been recognised at first. Prince Rupert imparted the secret of the process to Wallerant Vaillant, a native of Lisle, a portrait painter (born 1623, died 1677) who practised the method with great success, working chiefly at Amsterdam, and leaving to posterity many prints of considerable artistic merit. Sir Christopher Wren is also credited with the execution of one of the earliest mezzotints, a negro's head with a collar round the throat, but there is no satisfactory authority for the various statements to this effect, the only sound fact being that this early print is an extremely interesting specimen of the process. The first English engraving executed in this style _bearing a date_ is a portrait of Charles II. in an oval frame (Giul. Sherwin, fecitt 1669), by William Sherwin, who, there is some reason to believe, acquired his knowledge of the process directly from Prince Rupert. Sherwin, born about 1650, engraved also in line,[55] and is said to have had the distinction of engraver to the king conferred on him by patent, an exceptional honour. Among the mezzotinters about this period, Abraham Blootelingh, born at Amsterdam in 1634, and distinguished both as a line engraver and etcher, came over to England in 1673, made use of the method with admirable success, and is said to have effected considerable improvement in the process of laying the ground; his life-size head of the Duke of Monmouth, in an oval border or frame, is a masterpiece of the art. But, with the above exceptions, the works left by the majority of the early mezzotinters, both English and foreign, are more curious to the student than satisfactory to the artistic eye. It was not until the close of the century, when Isaac Beckett and John Smith had already begun to issue their grand series of portraits after Kneller, Lely, and other contemporary painters, that the full capabilities of the invention were realised and the foundation laid for the steady and uninterrupted progress of the art. John Smith's clear, bright, and intelligent face ought to be well known to Englishmen both from his own engraving and also from Kneller's admirable picture, from which it was taken, so long to be seen hanging in the Rubens and Rembrandt room of the National Gallery, and lately fittingly transferred to the National Portrait Gallery. He was a pupil of Beckett and native of Northamptonshire, and died at Northampton in 1742, where there is a tablet to his memory in St. Peter's Church.