Medford Historical Society Papers, Volume 15.

On the Upper Mystic.

Passers along Boston avenue, while crossing Canal bridge, frequently stop to view the river, the sweep of the parkway and the railway arches over both. But more are especially interested in the incessant bubbling in the river's surface, a little way down stream. Many conjectures are made as to its cause, some very fanciful. The majority attribute it to a subterranean spring, stronger than the river's flow. It was first observed some twenty years since, and is more noticeable since the building of the dam at Cradock bridge, and the consequent cessation of the tidal flow above said dam.

Comparatively few know that at this point a branch of the Metropolitan sewer passes beneath the river, and that air from within its siphon is forced through an imperfection in its masonry. It has been thus from its first use, and efforts to remedy the same have been unavailing.