There are two version of the book published in 1862 and 1864. Walker (1791-1867) had a career as an artist and engraver. The two versions differ in some respects. Both however have the same 51 people in the main part of the book but the second version has four additional names in an apprendix who are not included in the engraving. Walker does not make it clear why he included them in the second edition because three of them were dead before the 1807/8 date line of the book. Two subjects have no biography in either of the two editions of the book all though they appear in the first version of he engraving but not in the second.