Koning, the author of a prize essay on the invention of typography by Coster, expresses his belief in the theory that the types of the _Speculum_ were made from punches of wood and were founded in matrices of lead. His belief in the use of these rude implements is based on the well known fact that matrices of lead were frequently used by the earlier German and Dutch printers. Enschedé of Haarlem had in his type-foundry matrices of lead, which he claimed were used by Peter Schœffer in the fifteenth century. Firmin-Didot, the eminent [p302] type-founder of Paris, says that punches of wood and matrices of lead were used in his type-foundry for the casting of large ornamental types even as late as the beginning of the present century. His description is as curious as it is instructive. . . . I have often made use of this process, . . . which is to sink in lead, a character cut on wood, at the instant when, melted by heat, the lead is about to harden. Matrices of lead made by this process are subsequently justified for height and for lining, like other matrices. Then, by the ordinary process of stereotyping, one may take from this matrix, a duplicate in metal, which, after having been dressed, is replaced in the matrix in lead, and fitted up to a mould. The melted metal poured in this mould, not only makes the body of the type, but at the same time solders itself to the stereotype [nested in the matrix] which makes the face of the type. By this process one may take from a matrix in lead, a type as perfect as that which is obtained in the ordinary manner. But these matrices in lead will only make a limited number of stereotypes. . . . By taking the precaution to cool occasionally a matrix in lead, one can obtain from sixty to eighty types, without being obliged to re-enter the old matrix with the punch of wood, or to make a new matrix from the same punch. For vowels, and for the letters that are more frequently used, it is necessary to increase the number of matrices. But whenever the punch re-enters the matrix, the form of the punch undergoes some alteration from the effects of the pressure and the heat. It often happens that the punch is burned during the little time that it is buried in the hot metal. It then becomes necessary to re-engrave the punch. These are the reasons why differences in shape are to be found in the letters that are most frequently used.[159]