The relic which gives the best testimony of the mental powers of the Aztecs is their calendar, preserved for centuries from destruction, and now built into the cathedral of the city of Mexico. It was carved in the year 1512 A.D., and brought to the ancient Tenochtitlan from the spot where it was made. When it had nearly reached its destination, it broke down the floating bridge on which it was loaded, and was precipitated into the lake. The priest superintending the moving, and many of his assistants, were drowned, but it was raised with great difficulty from the water, and brought to the great temple located by Tizoc and Ahuitzotl, where it was inaugurated with human sacrifices. Not many years later this temple, like many others, was destroyed, and the huge calendar with other objects of heathen worship were buried in the surrounding marshes as the best way to get rid of them, by the order of the Christian priests. It lay hidden for two centuries, until the 17th of December, 1790, when the grade of the pavement in front of the cathedral was lowered, and it came to light. The Spanish Viceroy then controlling Mexican affairs allowed the commissioners of the cathedral to build it into their sacred edifice, on condition that it should be always preserved and exposed in a public place. It is now, however, considered as the property of the National Museum. This zodiac or calendar is twelve feet in diameter, made of a piece of basalt of immense weight. It gives a clear exposition of the division of time understood by the Aztecs, into cycles, years, and days. Fifty-two years constituted a cycle, the year had three hundred and sixty-five days, with five very unlucky intercalary days, wholly devoted to human sacrifice. Each year had eighteen months of twenty days each, and these months four weeks of five days each. The days had delightful names, such as "Sea Animal," "Small Bird," "Monkey," "Rain,"; not recurring every week, but different for the twenty different days of the month. The cardinal points were named "Reed," "House," "Flint," "Rabbit," for east, west, north, and south. Thus an Aztec might say, "I am going House on Sea-Animal," which would merely mean that he was starting for the west on Monday. The months likewise had descriptive names: thus the third month, which might correspond to our March, was called "Victims flayed alive," while the more agreeable title for the sixth month, which we call July, was "Garlands of corn on the necks of idols." As their writing was by pictures instead of by combinations of letters selected from an alphabet, they could give a long name in brief space with a few adroit turns of their writing instrument.