There is an old Mexican bridge near Tezcuco which seems to be the original _Puente de las Bergantinas_, the bridge where Cortes had the brigantines launched on the lake of Tezcuco. This bridge has a span of about twenty feet, and is curious as showing how nearly the Mexicans had arrived at the idea of the arch. It is made in the form of a roof resting on two buttresses, 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. The brigantines which the Spaniards made, and transported over the mountains in such a wonderful manner, fully answered their purpose, for without them Mexico could hardly have been taken. After the Conquest they were kept for years, for the good service they had done; but vessels of such size do not seem to have been used upon the lake since then; and I believe the only sailing craft at present is Mr. Bowring’s boat, which the Indians look at askance, and decidedly decline to imitate. It is true that, somewhere near the city, there is moored a little steamer, looking quite civilized at a distance. It never goes anywhere, however; and I have a sort of impression of having heard that when it was first made they got up the steam once, but the conduct of the machinery under these circumstances was so extraordinary and frantic that no one has ventured to repeat the experiment. Before we left Tezcuco, we went in a boat to explore Mr. Bowring’s salt-works, which are rather like the salines of the South of France. Patches of the lake are walled off, and the water allowed to evaporate, which it does very rapidly under a hot sun, and with only three-fourths of the pressure of air upon it that we have at the sea-level. The lake-water thus concentrated is run into smaller tanks. It contains carbonate and sesquicarbonate of soda, and common salt. The addition of lime converts the sesquicarbonate of soda into simple carbonate, and this is separated from the salt by taking advantage of their different points of crystallization. The salt is partly consumed, and partly used in the extraction of silver from the ore, and the soda is bought by the soap-makers.