1890-91.] LAKE CURRENTS. 157 



must be studied with reference to such matters. In your shore a similar 

 indentation is formed by Humber Bay, and you are right in advocating 

 a sewage outlet to the east, where the coast line is straight for a con- 

 siderable distance." 



But, however satisfying this theory may be to the scientist, it should 

 be put to the severest test before the least reliance is placed in it. And 

 I hope the city authorities will not allow the present season to go by 

 without ascertaining to the fullest possible extent the direction and 

 velocity of the lake currents, both deep and superficial, under all existing 

 circumstances. 



The result of the recent analysis of water from the bell buoy by 

 Professor Ellis, might be considered a staggering blow to the credulity 

 of those who had faith in the purity of the water from that source when 

 not contaminated with impurities from the bay through leakage into the 

 conduit, but not necessarily so. The rather does it show the danger 

 from western sewage outlets, and from the polluted waters of the bay. 

 It was very ably shown by, I think, a writer in the Mail, that the wind 

 rising in a certain quarter, and veering around to a different quarter, 

 would tend to bring the foul waters of the bay directly to the intake 

 pipe. This mechanical cause may have been aided by a phj'sical cause, 

 namely, the difference in temperature and consequently a difference in 

 density. Thus at the time the sample was taken the weather was 

 tolerably cold, the ice had just left the bay. The water in the 

 shallow portions inside the harbor is much more susceptible to changes 

 of temperature than in the deep water just outside the island. Suppose 

 the temperature of the water in the bay to be 39° Fah., its limit of 

 greatest density, and that outside to be 40°. Then as the water would 

 be driven out of the western gap as before described and around Light- 

 house Point, it would encounter the lighter waters of the lake and sink 

 beneath them, carrying down its load of sewage pollution to the bottom 

 to contaminate the water at the intake. But this state of things is not 

 irremediable. Cleanse the harbor, cut off the westerly sewage outlets, 

 and extend the intake pipe out to 70 feet of water and all danger will 

 vanish ; for it must be remembered that conditions may arise that would 

 contaminate the surface water at the location of the intake pipe which 

 would be perfectly harmless at a depth of 70 feet below. 



