444 Transactions of the Canadian Institute. [Vol. VII. 



June 30th. Changed all the water on the cedar sawdust to-day no 

 less than five times. Immediately after adding the fresh water black 

 bass fry were placed each time in the aquarium, and in each case the 

 animal was dead in from half an hour to forty minutes. 



July 7th. The last experiment with this sawdust was performed to- 

 day. The water was changed this morning at 9 a.m. for the thirty-first 

 time, and immediately afterwards a black bass fry was immersed in it. 

 It swam about below the floating bag which contained the sawdust. 

 The odour of the cedar was scarcely perceptible in the water. The 

 strength of the solution was, of course, increasing all the time. At 

 J I a.m. the fry was dead. 



Some of the water that was drained off from the sawdust at 9 a.m. 

 ■was found to contain 235 m.gs of solid matter per 1,000 c.c. Allowing 

 for the residue after ignition, there would still remain 155 parts per million 

 of poisonous extract dissolved out of the cedar cells in the thirtieth 

 •withdrawal. This is quite remarkable when it is remembered that the 

 •sawdust had been soaking continuously for five weeks, and the water on 

 •it changed thirty times. 



Comparing the solid in this solution with that in a saturated solu- 

 tion already given, viz., 1,240 per 1,000 c.c, we conclude that there has 

 'been a continuous withdrawal of poisonous extracts from the cedar. 

 The question, therefore, of v/hether a river is polluted with sawdust or 

 snot, simply becomes a question of determining the quantity of sawdust 

 ipoured into a known volume and flow of water, and the further question 

 'of determining whether the resulting solution is poisonous enough to kill 

 ifish eggs, fry, adult fish or fish food. 



Warm water was found to extract the poison from wood cells much 

 •,more quickly than cold water. 



Extracts from White Pine. 



The general effect of pine extracts upon fish eggs has already been 

 described. It only remains to point out some special effects under 

 varying conditions. One of these is that eggs live longer in aerated 

 sawdust water than in unaerated. This is quite clear from the following 

 experiment : At 9.45 a.m. of May i8th, two batches of eggs were placed 

 in pine water at the bottom of the aquarium. At 5.30 p.m. every egg 

 but two was dead. 



At 1 1. 1 5 a.m. of May 17th two batches were placed in pine water 

 .through which air was bubbling at the rate of 400 c.c. per minute. At 



