Illustrated Companion to the Latin Dictionary/Immissarium

This article incorporates text from a publication now in the public domain: Rich, Anthony (1849). The illustrated companion to the Latin dictionary, and Greek lexicon. p. vi. OCLC 894670115. https://archive.org/details/illustratedcompa00rich. 

IMMISSA'RIUM. A basin, trough, or other contrivance built upon the ground, of stone or brick, and intended as a cistern to contain a body of water flowing from the reservoir (castellum) of an aqueduct, for the accommodation of the adjacent neighbourhood. (Vitruv. viii. 6. 1.) It differs from cisterna, which was underground; and is shown by the annexed engraving (Immissarium/1.1), from a specimen at Pompeii. The high vaulted building is the reservoir, from which the water flowed through the small dark aperture at its bottom, into the square stone trough (immissarium) on the level of the pavement. The city of Pompeii is furnished with several other conveniences of this description.

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  Immissarium/1.1