observations with a minuteness of analysis which it is sometimes almost wearying to follow in print, and which nothing but the most enthusiastic love of truth and the most indomitable perseverance could have enabled him to execute in fact. Thus his conclusions are drawn from the monuments themselves; or rather, they are little more than a _résumé_ of the observations he has had to record upon those monuments. He has had before him, and, as far as possible, he sets before his readers, the precise situation and the measurements of all the crypts and galleries on all the different levels, and even of the thousands upon thousands of the individual tombs throughout this Christian necropolis; he marks the place and characteristics of every inscription, painting, and other monument he comes across in them; then, side by side with this immense mass of _data_, so important and so entirely trustworthy, he places every shred of old historical documents that he knows of, and which he thinks capable of throwing any light upon them; and finally proceeds to interpret them according to the very best rules of archæological criticism. The result has been a reconstruction of the history of the Catacombs, and in part also of their geography, in such perfect accord with all the facts and phenomena of the case, that there is probably no group of ancient monuments which can now be classified more exactly and with greater certainty than those in the Roman Catacombs. CHAPTER V. THEIR PAINTINGS AND SCULPTURE.