If the precipitate fails to dissolve, it is treated with aqua regia.
Ruins of it, as well as of the Aqua Claudia, exist at the present day.
A print from it, in aqua fortis, by Alessio Loyr, is mentioned Lett.
But if in the dissolving there be aqua fortis, it sufficeth to calcine it.
The reservoir was supplied with water by a branch aqueduct from the Aqua Marcia.