We were curious to see all that was to be seen; for Mr. Christy’s Mexican collection, already large before our visit, and destined to become much larger, contained numbers of implements and weapons of this very peculiar material. Any one who does not know obsidian may imagine great masses of bottle-glass, such as our orthodox ugly wine-bottles are made of, very hard, very brittle, and—if one breaks it with any ordinary implement—going, as glass does, in every direction but the right one. We saw its resemblance to this portwine-bottle-glass in an odd way at the Ojo de Agua, where the wall of the hacienda was armed at the top, after our English fashion, apparently with bits of old bottles, but which turned out to be chips of obsidian. Out of this rather unpromising stuff the Mexicans made knives, razors, arrow- and spear-heads, and other things, some of great beauty. I say nothing of the polished obsidian mirrors and ornaments, nor even of the curious masks of the human face that are to be seen in collections, for these were only laboriously cut and polished with jewellers’ sand, to us a common-place process. [Illustration: STONE SPEAR-HEADS AND OBSIDIAN KNIVES AND ARROW-HEADS, FROM MEXICO.] 1. Flame shaped Arrow-head; obsidian: Teleohuacán. 2. Arrow-head; opake obsidian: Teleohuacán. 3. Knife or Razor of Obsidian; shown in two aspects; Mexico. 4. Leaf-shaped Knife or Javelin-head; obsidian: from Real Del Monte. 5. Spear-head of Chalcedony; one of a pair supposed to be spears of State: found in excavating for the Casa Grande, Tezcuco. (This peculiar opalescent chalcedony occurs as concretions, sometimes of large size, in the trachytic lavas of Mexico.) Cortes found the barbers at the great market of Tlatelolco busy shaving the natives with such razors, and he and his men had experience of other uses of the same material in the flights of obsidian-headed arrows which “darkened the sky,” as they said, and the more deadly wooden maces stuck all over with obsidian points, and of the priests’ sacrificial knives too, not long after. These things were not cut and polished, but made by chipping or cracking off pieces from a lump. This one can see by the traces of conchoidal fracture which they all show.