ed as a metallic ore. It was ascertained empirically that fusing copper in contact with a certain stone gave it a yellow color, and the result — brass — was highly valued.
Aristotle and Strabo refer to this earth, as do also Ambrosius, Bishop of Milan, fourth century; Primasius, Bishop of Adrumetum, in Africa, sixth century; and Isidore, Bishop of Seville, seventh century.
These learned prelates mention an addition by which copper acquired a gold color.
This was undoubtedly calamine.
Albeed for the entrance of the vessel, and restored again to form a dam to preserve the upper level.
Movable gates to restrain the water on the higher level and admit the passage of boats were introduced in the navigation of the Tesino and Adda to Milan.
Cresy dates the invention of canal-locks to 1188, when Pitentino restored the Mincio to its ancient channel to the Po, from whence it had been diverted by the Romans in the time of Quintus Curtius Hostilius.
The canal of Languedoc, which u