TRANSACTIONS OF THE SECTIONS. 245 



of that of the -wheel itself, if placed at its extreme radius, would produce an 

 oscillation of Ijin. in range, and which would continue for many minutes ; or if 

 the -wheel -were moved 90 degi-ees from its position of rest, the oscillations -would 

 continue for nearly twenty minutes, the movement being so slo-w and solemn as to 

 impress on the mind of an observer -who had not seen it put in motion that the 

 action -was self-orig-inated or induced b}' some mysterious agency. The oscillation 

 of a ship could not put such a -wheel in motion; or rather, if an infinitesimal 

 motion were produced, this would be of so long a period that its effects would be 

 easily separable from those proper to the oscillation of the ship. Thus the 

 indications would be more exact than those produced by the rocking-arm on deck. 

 The apparatus last described on deck had not yet been tried, and was awaiting a 

 good rough day at Plymouth. 



The Brigliton Intercepting and Outfall Seivers. By John G. Gamble, B.A. 



Plitherto the sewage of Brighton has been partly received by cesspools, partly 

 carried by various outfalls direct into the sea. The cesspools are being gradually 

 abolished ; but although nearly all the present outfalls now discliarge under the 

 sea beyond low-water mark, yet the nuisance to bathers and to people in boats is 

 considerable. The intercepting sewer designed by Mr. Hawkshaw, C.E., and at 

 present in course of construction, will intercept all the existing outfalls, and will 

 cany the sewage away to the eastward four miles from the nearest point of 

 Brighton, where it may either be discharged into the sea or utilized. Float experi- 

 ments undertaken olf Portobello prove that no nuisance can possibly be caused to 

 Brighton. 



The sewer is of circular section throughout, being of 5 feet internal diameter for 

 nearly t-wo miles, and 7 feet internal diameter for more than seven miles. The fall 

 is 3 feet per mile. 



At some to-wns the sewers are required to act as land-drains as well as sewage- 

 carriers. This very objectionable plan is not necessary at Brighton, as the land 

 water sinks down into the chalk, and comes out on the shore at low tide without 

 troubling the basements of the houses. The sewer has, on the contrary, to be made 

 especially water-tight, so as to resist the percolation from the porous strata without 

 as well as any leakage from within. The storage capacity is such that if the whole of 

 twelve hours' flow were penned up in the sewer it would not reach within a mile 

 of the east end of Brighton, and any gases generated would pass up ventilating- 

 shafts more than a mile from the town. A stomr overflow and a flushing inlet 

 will be provided. The great difficulty in managing sewers is to keep them clear of 

 the road-sweepings, which get past the gulleys, form a solid deposit in the sewer, 

 and collect other and more noxious materials upon them. In sewers of short 

 length flushing by water is the best method of getting rid of such deposit ; but in 

 the case of a sewer more than seven miles long the expense of flushing the deposit 

 forward and forward to the outfall, as well as the damage thereby done to the brick- 

 lining, would be so great that probably the greater part of the solid materials will have 

 to be removed by hand at the various entrances. To assist this, catch-tanks will be 

 placed at all junctions, to stop as much as possible of the road-drift, flints, &c. that 

 would otherwise get into the sewer. Wherever possible road-gulleys ought not 

 to discharge into the sewers ; in the front of Brighton they might, and some do, 

 discharge on to the beach. No objection could be made to this if a good sj'steni 

 of scavenging for horse-droppings were in operation. Yentilating-shafts are placed 

 at intervals ; they are covered by cast-iron grates made in two portions, one 

 fltting inside the other. This is important, as a man or boy can remove the inner 

 casting without disturbing the road metalling. He can thus get into the catch- 

 pit with which all these shafts are provided, and clear out anj' road-sweepings that 

 may have fallen through the grating. Charcoal baskets are not used, as it has 

 been proved that they check the current of air. Charcoal will no doubt purify 

 air that is forced through it, but it is only in winter when the sewer air is warmer 

 than the air without that any great current is created. Besides, the air inside 

 being generally cooler and therefore heavier, sulphuretted hydrogen and carbonic 

 acid gas, two of the sewer gases, are both heavier than air j hence the only escape ie 



