1890-91.] SEVENTEENTH MEETING. 31 



outfall can be obtained into the sea or other large body of water that is 

 the cheapest way of disposing of sewage. Indeed, a novel method is 

 proposed for the city of London, namely, to transport it in steamships 

 constructed for the purpose out into the channel and dump it into the 

 sea. This is supposed to be the most speedy, cheap, and cleanly way of 

 disposing of it. 



Where places are situated on tidal waters these can be utilized for the 

 purpose of scouring the outlet pipe and carrying all offensive matters far 

 out to sea. It was a consideration of the foregoing methods of sewage 

 disposal, of which Portsmouth, England, affords a good example, which 

 led Mr. Clark to devise a scheme which would secure the advantages of 

 tidal waves and avoid the expense of pumping. By means of a high- 

 level sewer along Gerrard street, extending from Vonge to Parliament 

 streets, connected with a large automatic flushing tank, a head of 32 feet 

 could be secured instead of 10 to 12 feet, the ordinary height of the tides 

 around England. Then instead of twice a day the flushing could take 

 place every hour in the day if desirable. From four to eight large 

 flushes of half a million gallons each would be ample to keep the outlet 

 pipe scoured. 



Mr. Clark showed by illustration on the blackboard why deposits take 

 place in sewers that are constructed too large. He also explained a 

 formula of his own by which to determine the velocity of sewage flowing 

 in sewers partly full. This is a fact too often lost sight of, and to which 

 is attributable many of the present defects in drainage. 



Mr. Clark also read a paper, " A Few Words on Lake Currents." He 

 held that there are no regular, constant, well-defined lake currents, but 

 that these are variable, dependent on the conformation of the shore and 

 the storms that affect the surface. This is important in view of the 

 proposal to discharge our sewage into the lake. The effect of a con- 

 tinued strong easterly gale is to drive the surface water to the west, 

 where it piles up on the shores at the western end at Hamilton beach, 

 and by the head thus produced a portion of the water is forced back- 

 ward as an undertow, thus producing a current in the opposite direction 

 to the waves on the surface. This undercurrent then in flowing to the 

 east would first pass the intake of Toronto water supply, and then pass 

 the contemplated place of discharge of sewage, so that a sewage outfall 

 to the east would in no way endanger the water supply. When the 

 winds were in the contrary direction it would not produce a counter- 

 current below, as the outlet is towards the east, and as the waters flow 

 down the lake they would make their exit by the St. Lawrence. This 

 makes plain the danger that would arise from having sewage disposal 

 outlets to the west. 



