The _Corpus Inscriptionum_ had not at that time got very far, but its first volume, edited by Mommsen, contained the ancient Fasti, which supply us with the religious calendar of early Rome, and with other matter throwing light upon it. This first volume was an invaluable help, and formed the basis (in a second edition) of the book I was eventually able to write on the _Roman Festivals of the Period of the Republic_. At that time, too, in the 'eighties, Roscher's _Lexicon of Greek and Roman Mythology_ began to appear, which aimed at summing up all that was then known about the deities of both peoples; this is not even yet completed, and many of the earlier articles seem now almost antiquated, as propounding theories which have not met with general acceptance. All these earlier articles are now being superseded by those in the new edition of Pauly's _Real-Encyclopaedie_, edited by Wissowa. Lastly, Wissowa himself in 1902 published a large volume entitled _Die Religion und Kultus der Roemer_, which will probably be for many years the best and safest guide for all students of our subject. Thoroughly trained in the methods of dealing with evidence both literary and archaeological, Wissowa produced a work which, though it has certain limitations, has the great merit of not being likely to lead anyone astray. More skilfully and successfully than any of his predecessors, he avoided the chief danger and difficulty that beset all who meddle with Roman religious antiquities, and invariably lead the unwary to their destruction; he declined to accept as evidence what in nine cases out of ten is no true evidence at all--the statements of ancient authors influenced by Greek ideas and Greek fancy. He holds in the main to the principle laid down by Marquardt, that we may use, as evidence for their religious ideas, what we are told that the Romans _did_ in practising their worship, but must regard with suspicion, and subject to severe criticism, what either they themselves or the Greeks wrote about those religious ideas--that is, about divine beings and their doings.