“The house at the corner of a street at the south-east of the great square is built upon and in part supported by a fine circular altar of black basalt, ornamented with the tail and claws of a gigantic reptile. In the cloisters behind the Dominican Convent is a noble specimen of the great serpent idol, almost perfect, and of fine workmanship; this monstrous divinity is represented in the act of swallowing a human victim, which is seen crushed and struggling in its horrid jaws. “The only works of art of the inhabitants of the city of Mexico before the conquest, then called Tenochtitlan, now publicly seen, are the great Calendar Stone, popularly called Montezuma’s watch, and the Sacrificial Stone, or the grand altar, once standing in the great temple before the principal idol. The former measures twelve feet in diameter, and is cut from one large block of porous basaltic stone. It is supposed to have been placed in the roof of the great temple in the same manner as the Zodiac was in the temple of Tentyra in Upper Egypt.[65] It now stands against the north-west wall of the cathedral, and is an attractive object of antiquarian research, and a striking proof of the perfection the nation to which it belonged had attained in some of the sciences; few persons, even of the most enlightened cities of Europe, of the present day, would be capable of executing such a work. “From the first moment I beheld it I determined, if possible, to convey to Europe a fac-simile of so fine a specimen of Aztec skill. Through the influence of Don Lucas Alarman, the prime minister, I obtained permission of the clergy to erect a scaffold against the cathedral, and took an impression of it in plaster, which was afterwards carefully packed up, and with some difficulty conveyed to Vera Cruz. It has fortunately arrived safely in England, and now forms one of the subjects of the exhibition of Ancient Mexico to be seen in the Egyptian Hall. “The Sacrificial Stone, or altar, is buried in the square of the cathedral, within a hundred yards of the Calendar Stone. The upper surface only is exposed to view, which seems to have been done designedly. As I had been informed that the sides were covered with historical sculpture, I applied to the clergy for the further permission of having the earth removed from around it, which they not only granted, but moreover had it performed for me at their own expense. “I then took casts of the whole. It is twenty-five feet in circumference, and consists of fifteen groups of figures, representing the conquests of the warriors of Mexico over different cities, the names of which are written over them.