The study of the question of the invention of printing, like that of any other historical question, must deal with the examination of three classes of evidence or so many of them as may be available. These three classes of evidence, in order of their importance, are first, remains, second, contemporary documents, and third, documents or evidence of a later period. For example, there may be tradition widely current and running backward in literary form to within a hundred years of the death of the person referred to, that a certain king ruled in a certain country and did certain things. That is evidence of the third class. There may be extant contemporary works of travelers, histories of other countries, or even the published recollections of old men, which said that at a certain period that king lived and did certain things. That is evidence of the second class. There may be coins, official inscriptions, public documents, emanating directly from this king or even bearing his signature. This is evidence of the first class. This class of evidence is conclusive. The second class is strong, but not conclusive, the third class is very uncertain. Now it happens that with regard to the invention of printing we have evidence of all three classes. All of it is conflicting, but the conflicts, it is to be noted, are mainly in the evidence of the third class. The evidence of the second class exists mainly in Mainz, but is not nearly as conclusive as has been supposed. Evidence of the first class comes entirely from Haarlem, and is there supported by one or two important pieces of evidence of the second class. With this brief introduction perhaps it will be easier to understand the argument which follows. Of course, the material of the first class, namely, remains, would be the earliest known pieces of printing. If these pieces of printing were dated as books are today, they could not be questioned, but as they are not so dated, but must be placed by other evidence, they have been questioned. There exist, in whole or in part, forty-seven distinct pieces of printing each bearing evidence of being among the first pieces of printing produced. These forty-seven works in their present condition run all the way from an entire book to a fragment of a single page. A group of three or four of them may be identified by reference to officials whose official dates were known as being either in 1474 or immediately preceding it. This, however, does not date the whole group. These few specimens are much more advanced in their appearance and workmanship than the rest of the forty-seven. Several other editions of some at least of these better books appear in this interesting lot of remains. The other editions are of a much more primitive appearance, showing that the period covered by the forty-seven works ended not later than 1474.