hes, or it may be feet aboveground, and terminating it with an earthenware capwith charcoal tray under as at b ; see fig. 32c. Again, as for instance in the grounds appertainingto a large public building, where from the very lengthof the drains there must be a generation of some foulgas, a… … England. A much larger ventilator, suitable forerection over a square shaft, and very well adapted tothe larger drain-pipes, is given at fig. 34, and here thecharcoal is laid upon a portable spiral tray. The rainor road-water enters in at the annular gratings outside,and when the grit box is full,…
