[2663] See B. ii. c. 106, and B. iii. c. 17. In order to check the sudden rise of its waters, a design was entertained by Julius Cæsar to construct a subterranean canal from the lake into the valley of the Liris, which, unfortunately, was frustrated by his death. Claudius, however, executed the work, by cutting a gallery upwards of an English mile and a half through the limestone rock; a work which, according to Suetonius, occupied thirty thousand workmen continually for eleven years. On opening it with a mock naval combat, an accident happened in which many persons lost their lives, and Claudius himself but narrowly escaped. The emissary answered its purpose for some time, and, though Nero suffered the works to fall into decay, they were repaired by Hadrian. In the middle ages, however, the work fell in, and has not since been restored.
[2664] See B. iii. c. 9.
[2665] “Magnes.”
[2666] In Chapter [23] of this Book.
[2667] “Iron earth;” from σίδηρος, “iron.” The magnet, or loadstone itself, is an oxide of iron, known as Oxidulated iron, or Ferroso-ferric oxide; sometimes in combination with quartz or alumine.
[2668] From Heraclea, in Lydia, or in Thessaly, according to some accounts. It is not improbable, however, that it was so called after “Heracles,” or Hercules, on account of its powerful influence upon iron ores.
[2669] Isidorus says, “India,” in B. 16 of the “Origines.”
[2670] See the list of authors at the end of this [Book].
[2671] Varieties, no doubt, of oxide of iron.
[2672] An absurd distinction, as Ajasson remarks; based, probably, on Eastern notions, and with reference to the comparative powers of attraction.