The general opinion is that the cromlechs were altars on which the priests offered their dreadful sacrifices. On this subject Cæsar has the following remarks:—“The whole nation of the Gauls, (whom Cæsar describes as imitators of those of Britain, and as deriving from the latter their customs) is much addicted to religious observances, and on that account, those who are attacked by any of the more serious diseases, and who are in danger of warfare, either offer human sacrifice or make a vow that they will offer them, and they employ the Druids to officiate at their sacrifices; for they consider that the favour of the immortal gods cannot be conciliated, unless the life of one man be offered up for that of another; they have sacrifices of the same kind appointed on behalf of the state.” To which we may add, that Tacitus, in his account of the Roman attack on the Isle of Anglesey, the then great stronghold of the British Druids, states—that “they held it right to smear their altars with the blood of their captives.” It is a striking corroboration of the theory that the cromlechs were the altars on which these dreadful sacrifices were performed, to find that in this very Isle of Anglesey are yet existing about thirty, among which are some of the largest and most magnificent our country possesses. It is well known that, at a very early period, this Island was the great school of Druidism—the chosen retreat and asylum of the Druidical Priests. No wonder, therefore, that travellers are particularly struck with the great absence of trees, having naturally enough supposed that the former scene of Druidical superstition, the horrors of which were carried on in the dark recesses of consecrated groves, would not be so bare and destitute of timber. Nor did Anglesey always wear this naked appearance. Classical authors tell us it formerly had its venerable woods and shady groves, and the ancient British appellation _Ynys Dywyll_, or the Shady Island, intimates the same fact; and bodies of trees are constantly met with in the pits from which the inhabitants get their peat. Having made these remarks we shall now direct the attention of the tourist to the TREFIGNETH CROMLECHI.