EFFECTS OF SAWDUST ON FISH LIFE 



39 



SESSIONAL PAPER No. 22a 



dogmatic statements of their own, but simply submitted the statements of witnesses 

 whom they had examined. 



The experimental part of my work was begun at the Dominion Biological station, 

 St. Andrews, N.B., in 1900, and has been continued since then in the biological labora- 

 tory of Queen's University, Kingston, Ontario. The river work consisted of a few 

 weeks' study of the Bonnechere, a tributary of the Ottawa. 



Those who are interested in the details of my experimental work are referred to 

 the Transactions of the Canadian Institute, Vol. VII., 1903, under the article * Saw- 

 dust and Fish Life.' 



SINKING OF SAWDUST. 



Numerous observations were made upon the sinking of sawdust. The general 

 method of experimentation was to add known volumes of sawdust from different kinds 

 of wood to separate vessels containing a measured volume of water. The sawdust was 

 generally dropped quietly upon the top of the water. As a rule, the particles of saw- 

 dust began to sink the moment the sawdust touched the water. This was particularly 

 true if the particles were fine; but there were considerable variations in the rapidity 

 with which sinking occurred. So far as could be determined by laboratory experi- 

 ments, the rate of sinking varied with (a) the size of the dust particles, (h) the way 

 in which they were made, (c) the motion of the water, (d) the dryness of the dust, 

 and (e) the kind of wood. 



Large particles sink more slowly than small ones, because the latter are more 

 easily penetrated by the water. 



Large saws which strike logs with great force (as in a sawmill) compress the 

 wood, drive out the air imprisoned in the cells, and produce sawdust that sinks 

 quickly. 



Sawdust sinks slowly in perfectly calm water, such as a standing vessel. If the 

 vessel be tapped gently on the side, the sawdust sinks much more quickly. 



If thrown into rapidly flowing stream, sawdust is carried downwards until it 

 reaches pools, eddies, or comparatively calm stretches; it then sinks and forms saw- 

 dust beds. Some of these are of great extent along the Ottawa river. 



Sawdust from different kinds of wood arranged themselves in the following order 

 as regards rate of sinking. — 



1. Oak. 



2. White pine, 50 to 80 per cent of it in 2 or 3 minutes. 



3. Maple. 



4. Cedar. 



5. Elm. 



But it must be remembered that the particles in my experiments differed from 

 each other in size and in the moisture they contained, and consequently different 

 results might easily be obtained by other observers. The important point is that 

 all kinds of sawdust sank in a few minutes in agitated water. 



EXTRACTS FROM SAWDUST. 



When sawdust was placed in a clean bag, and the bag sunk to the bottom of an 

 aquarium by means of stones, there oozed out of the sawdust a yellowish, brown liquid 

 which lay along the bottom of the vessel. (See fig. 1). In a number of experiments 

 this brownish water occupied If inches at the bottom of an aquarium containing 

 water to a depth of 16^ inches. The overlying water remained clear and colourless for 

 several days when pine sawdust was used. In the case of cedar, the aqueous extract 

 diffused upwards into the clear water, but never rendered it so dark aa that which lay 

 at the bottom. When the brown water was siphoned out, the sawdust soon dis- 

 coloured more of the clear water. Evidently the water was dissolving out from the 



22a— 6i 



