All this material has been collected, sifted, and built upon by modern scholars, and chiefly by Germans. The work of collecting was done to a great extent in the sixteenth and seventeenth centuries; the rest of the process mainly in the nineteenth. The chief writers will be quoted as occasion demands; here can only be mentioned, _honoris causa_, the writings of Ambrosch, Preller, Schwegler, Marquardt[46], and of some of the writers in the _Mythological Lexicon_, edited by Roscher, especially Professor Wissowa of Berlin, whose short but pithy articles, as well as his treatises _de Feriis_ and _de Dis Indigetibus_ are models of scholarly investigation[47]. Of late, too, anthropologists and folk-lorists have had something to say about Roman religious antiquities; of these, the most conspicuous is the late lamented Dr. Mannhardt, who applied a new method to certain problems both of the Greek and the Roman religion, and evolved a new theory for their interpretation. Among other works of this kind, which incidentally throw light on our difficulties, the most useful to me have been those of Professor Tylor, Mr. Frazer, Mr. Andrew Lang, and the late Professor Robertson Smith. In the _Religion of the Semites_, by the last named scholar, I seem to see a deeper insight into the modes of religious thought of ancient peoples than in any other work with which I am acquainted. Yet in spite of all this accumulation of learning and acumen, it must be confessed that the study of the oldest Roman religion is still one of insuperable difficulty, and apt to try the patience of the student all the more as he slowly becomes aware of the conditions of the problem before him. There are festivals in the calendar about which we really know nothing at all, and must frankly confess our ignorance; there are others about which we know just enough to be doubtful; others again, in interpreting which the Romans themselves plainly went astray, leaving us perhaps nothing but a baseless legend to aid us in guessing their original nature. It must be borne in mind that the Roman religion was in ruins when the Julian calendar was drawn up, and that the archaeological research which was brought to bear upon it by Varro and Verrius was not of a strictly scientific character. And during the last two centuries of the Republic, as the once stately building crumbled away, it became overlaid with growths of foreign and especially of Greek origin, under which it now lies hopelessly buried. The ground-plan alone remains, in the form of the calendar as it has been explained above; to this we must hold fast if we would obtain any true conception of the religion of the earliest Roman State[48]. Here and there some portion of the building of which it was the basis can however still be conjecturally restored by the aid of Varro and Verrius and a few other ancient writers, tested by the criticism of modern scholars, and sometimes by the results of the science of comparative religion.