CHAPTER VI. TEZCUCO.

and composed of slabs of stone with the edges upwards, with mortar in the interstices; the slabs being sufficiently irregular in shape to admit of their holding together, like the stones of a real arch. One may now and then see in Europe the roofs of small stone hovels made in the same way; but twenty feet is an immense span for such a construction. I have seen such buildings in North Italy, in places where the limestone is so stratified as to furnish rough slabs, three or four inches thick, with very little labour in quarrying them out. In Kerry there are ancient houses and churches roofed in the same way. What makes the Tezcuco bridge more curious is that it is set askew, which must have made its construction more difficult.