450 



Transactions of the Canadian Institute. 



[Vol. V^II. 



minnows lived only from three to five minutes. Outlet. 



When the fresh water entered at the rate of 125 c.c. 



per minute, minnows lived from twenty to ninety 



minutes. The control animals were kept for a week 



in a similar bottle, without sawdust, of course, and 



with water coming in at the rate of 1 10 c.c. per minute. 



In these experiments the poisonous extracts must 



have been coming away all the time. The moment 



the bottle was full of water the minnows were 



slipped into it. Consequently, when the fish were 



killed in five minutes, the 600 c.c. at first in the bottle. 



and 400 c.c. additional water were poisoned. When 



they were killed in ninety minutes, no less than 11,250 



c.c. were poisoned. That is, the percentage weight of sawdust to 



poisoned water was .16 per cent. This determination is important, as 



we shall see later, when we come to compare it with the percentage of 



sawdust thrown into the Bonnechere River. 



FIG. 



Fish at Mill-ends. 



Millmen and anglers alike testify that many kinds of fish are taken 

 by hook and line at mill-ends, no matter how excessive the sawdust may 

 be. The sawdust does not kill the fish so long as there is a rapid and 

 abundant flow of water. Why do fish thus congregate at mill-ends ? 

 To answer this question we must remember two things : first, rapidly 

 running water is better aerated than sluggish water ; and secondly, some 

 fish, such as trout and salmon, ascend streams until they reach suitable 

 spawning grounds, or are stopped in their ascent by high falls or mill- 

 dams. In ascending a river these fish are but obeying a law of their 

 nature ; in congregating at mill-ends they are equally obeying a law of 

 their nature, and are instinctively seeking water which furnishes their blood 

 with a plentiful supply of oxygen. This instinct is well illustrated in 

 the experiment just described in Fig. 3. The experiment was repeated 

 a number of times, and in every instance the fish discovered where the 

 fresh water came in. In one instance, in order to get close to the in- 

 coming water, a minnow stood on its head for fifteen minutes with more 

 than half of its body buried beneath the sawdust. It was thus acting 

 under the impulse of two fundamental instincts, viz., the instinct to avoid 

 poisoned water on the one hand, and to seek fresh water on the other. 

 The experiment seems to throw light upon the experience of anglers who 

 have found that trout desert the main stream when saw mills are running, 

 and betake themselves to the unpolluted branch streams lower down. 



