642 PROCEEDINGS OF SECTION J. 



curves through the circular openings at the ends of the weir wall, 

 and thence it flows through the outlet channels to the sea. The 

 lines of the outlet channels and general arrangements are such 

 that waves rushing up either outlet, after crossing obliquely the 

 lines of flow of the sewage, expend their force on the weir wall, 

 and are deflected by it down the other outlet, or upwards in the 

 chamber if a heavy sea happens to rush up both outlets at the 

 same time, an event which seldom happens, as the northern outlet 

 dischni'ges in a recess in the clifl', sheltered from easterly and south- 

 easterly winds. The ogee fall, the work in the chamber, to a height 

 varying from eight feet to fourteen feet, and the lining of the 

 outlet channels is constructed of blue-stone ashlar, packed solid to the 

 rock with blue-stone concrete. The upper portion of the chamber is 

 lined with blue-stone concrete, keyed in the arch with brickwork and 

 the shaft from the top of the chamber arch to the surface is lined 

 with brickwork packed solid to the rock with concrete. The 

 voussoirs in the outlet channels are twelve inches in depth, except 

 for a length of twelve feet at the outer ends, where the depth is 

 eighteen inches ; and this length of twelve feet is bolted together 

 by longitudinal bolts, passing in grooves cut in the voussoirs, 

 between a heavy annular casting, covering the outer end, and large 

 washers at the other end, so as to bind the length into one solid 

 mass, washers being used at the inner end so as to allow of a good 

 bond being kept in the masonry. To guard against the contingency 

 of the four feet openings in the weir wall becoming choked by any 

 rubbish which might by any possibility get into the sewer, the 

 height of the centre part of the weir is fixed so that the sewage 

 would flow over it before any pressure would be brought on the 

 main sewer. Any rubbish which may pass through the openings 

 in the weir wall is certain to pass through the outlets, considering 

 the action of the waves, so that no obstruction of the outlets from 

 such cause is considered possible. Arrangements are made whereby 

 workmen can descend the shaft and inspect the chamber, and do 

 any raking or grappling, from a platform at a safe elevation, 

 which might be necessary. Grooves are also provided for stop- 

 boards by means of which either outlet or portions of the chamber 

 can be shut oft" for examination or repair. In driving the northern 

 outlet channel, a length of a few feet of rock was left in to keep 

 out the sea during the lining of the channels and chamber, and 

 the sea was kept out of the other channel by putting in a dam. 

 When the work was thoroughly set, the channels were opened 

 out. The height of the shaft from the chamber floor to the surface 

 of the ground is one hundred and forty-tive feet. The top of the 

 shaft is protected by a stone wall enclosure with an iron door, and 

 an open iron grating roof over the enclosure, not visible from the 

 outside. The rush of air and spray caused by the dashing of the 

 waves into the chamber is deflected by the weir wall of this shaft. 

 The author has seen the outlet at work, and it seems to him to 



