440 Transactions of the Canadian Institute. [Vol. VIL 



this latter case the poisons come away so slowly that air (oxygen), sun- 

 light, and bacteria have ample time in which to change their poisonous 

 character ; whereas in the saw mill, the pulp mill, and the beet sugar 

 factory, the poisons are quickly discharged into running water, and 

 tend at once to produce their effects upon fish and other life. 



Strength of Sawdust Extracts. 



As already explained, the first experiments were made with solu- 

 tions obtained by soaking white pine sawdust for at least twenty-four 

 hours in tap water from Lake Ontario. When the sawdust was soaked 

 for four days in tap water, i,ooo c.c. of the yellowish-brown solution 

 already de'scribed as oozing out from the bag of sawdust, and lying at 

 the bottom of the aquarium, yielded 1,240 milligrams of solid matter 

 after evaporation in a platinum crucible. The ash from this weighed 80 

 m.gs., which was found to be exactly the same as that from tap water. 

 Deducting this from 1,240, leaves 1,160 m.gs. as the weight of the 

 material stored in the pine cells of the sawdust, and dissolved out in 

 1,000 c.c. of water in four days. 



After filtering off the first water, and adding fresh water to the 

 same sawdust, and allowing the mixture to stand five days longer, it was 

 found that 1,000 c.c. of this second solution yielded a total of 360 m.gs. 

 of solid, or allowing for the ash in tap water, a net residue of 260 m.gs. 

 of reserve material was dissolved out the second time. 



The corresponding figures for cedar (Ontario) sawdust were as 

 follows : — 



1. Solid from i,ooo c.c. soakingf four days ii300 m.gfs. 



2. Same sawdust with first water filtered off, fresh water 



added and allowed to stand five days =55° m.gs. 



3. Same operations repeated, soaking five days =350 m.gs. 



No allowance is made in these figures for the ash from tap water, 

 viz., 80 m.gs. 



These figures indicate clearly enough that the reserve material 

 stored in the wood cells comes away in diminishing quantities every 

 time fresh water is added to the sawdust. 



The next point sought to be determined was the number of times 

 that fresh water could be added to a fixed weight of sawdust and con- 

 tinue to produce solutions which would be poisonous to fish life. For 



