The Mask of wood is covered with minute pieces of turquoise—­cut and polished, accurately fitted, many thousands in number, and set on a dark gum or cement.  The eyes, however, are acute-oval patches of mother-of-pearl; and there are two small square patches of the same on the temples, through which a string passed to suspend the mask; and the teeth are of hard white shell.  The eyes are perforated, and so are the nostrils, and the upper and lower teeth are separated by a transverse chink; thus a wearer of the mask (which sits easily on one’s face) can see, breathe, and speak with ease.  The features bear that remarkably placid and contemplative expression which distinguishes so many of the Aztec works, in common with those of the Egyptians, whether in their massive stone sculptures, or in the smallest and commonest heads of baked earth.  The face, which is well-proportioned, pleasing, and of great symmetry, is studded also with numerous projecting pieces of turquoise, rounded and polished.

In addition to the character of the work and the style of face, the evidence of the Aztec origin of this mask is confirmed by the wood being of the fragrant cedar or cypress of Mexico.  It may be remarked also that the inside is painted red, as are the wooden masks of the Indians of the North-west coast of America at the present day.

The Knife presents, both in form and substance, more direct evidence of its Aztec origin; for, in addition to its incrustation with the unique mosaic of turquoise, blended (in this case) with malachite and white and red shell, its handle is sculptured in the form of a crouching human figure, covered with the skin of an eagle, and presenting the well-known and distinctive Aztec type of the human head issuing from the mouth of an animal. (See cut, p. 101.) Beyond this there is in the stone blade the curious fact of a people which had attained to so complex a design and such an elaborate ornamentation remaining in the Stone-age; and, somewhat curiously, the locality of that stone blade is fixed, by its being of that semi-transparent opalescent calcedony which Humboldt describes as occurring in the volcanic districts of Mexico—­the concretionary silex of the trachytic lavas.

The second Mask is yet more distinctive.  The incrustation of turquoise-mosaic is placed on the forehead, face, and jaws of a human skull, the back part of which has been cut away to allow of its being hung, by the leather thongs which still remain, over the face of an idol, as was the custom in Mexico thus to mask their gods on state-occasions.  The mosaic of turquoise is interrupted by three broad transverse bands, on the forehead, face, and chin, of a mosaic of obsidian, similarly cut (but in larger pieces) and highly polished,—­a very unusual treatment of this difficult and intractable material, the use of which in any artistic way appears to have been confined to the Aztecs (with the exception, perhaps, of the Egyptians).