At Crannon[1] there are certain hot springs, though not at boiling heat, the water of which, mixed with wine, preserves it warm in the vessels for a period of three days. The same is the case, too, with the springs of Mattiacum[2] in Germany, beyond the river Rhenus, the water of which retains its boiling heat three days. The margin of these springs is covered with pumice, formed by the action of the water.