Whether the types of the unknown printer were founded entirely in sand, or in matrices of lead, cannot be positively determined from the appearance of the letters, for it seems that either method of founding would produce types showing similar defects. It is probable that the punches were cut on wood, and sunk in hot metal as described by Didot, and that the types of the _Speculum_ were not only cast in lead matrices, but that the matrices were sometimes conjoined, and that two or more letters were cast together on one body. There is a closeness of fitting in some of the words which cannot be [p303] explained with entire satisfaction by the hypothesis that this closeness is the result of flattening out under pressure. One is strengthened in this belief when he discovers that it was not an uncommon practice in the type-foundries of the fifteenth century to join the matrices. Six of the matrices owned by Enschedé, and by him attributed to Schœffer, were made to be combined. These leaden matrices were pierced through their sides with a gimlet-hole, in which an iron wire was inserted to bind them together, and keep them securely on the mould. The method was faulty, for it could not keep the matrices in proper position; it could not produce types uniform as to height and true as to line.[160] The thick faces and flattened lines of the types in many of the unknown printer’s books show that his types were of very soft metal, probably of pure lead. To satisfy his doubts on this subject, Enschedé cast in some of his antique moulds types composed almost entirely of lead. The experiment succeeded: he was convinced that practical types of lead could be founded in matrices of lead.[161] Blades carried this experiment to a more successful conclusion, for he put the types to practical use. He had cast for him a collection of types in [p304] “unmixed lead,” with which he printed five hundred impressions on rough and dry paper. He says that the types showed no appreciable wear; but this is not surprising, for we have evidences that they were printed by an expert pressman on an iron press provided with every appliance requisite for a nice adjustment of the impression.