History of Sanitation

HISTORY OF SANITATION 23 which access could be had to the channel to make repairs. When two or more channels were carried one above another, the vent holes of the lower ones were placed in the sides. When possible, aqueducts were carried in a direct line, but frequently they were given a tortuous course either to avoid boring through hills, where their construction would have entailed too great expense, or else to avoid very deep valleys or soft marshy ground. In every aqueduct, besides the principal reservoirs at its mouth and terminal, there were intermediate ones at certain distances along its course, in which any remaining sediment might be deposited. In addition to serving as sediment basins, these reservoirs made it more easy to superintend and keep in repair the different sections, and provided service reservoirs to furnish irrigation water for fields and gardens and water for stock. The prin- cipal reservoir was that in which the aqueduct ter- minated. This reservoir or castella, as it was called, far exceeded any of the others in grandeur of arch- itecture, or in magnitude and solidity of construction. Water Tower and Roman Ruins, Chester, England