1902-3.] Sawdust and Fish Life. 447 



June 30th. A slight modification was made in this experiment. In 

 place of siphoning off the strong extract at the bottom of the aquarium, 

 the whole 7,000 c.c. of water were drained off, and the aquarium was 

 filled up with fresh water. The weights were removed from the bag> 

 which at once rose to the top of the water. Consequently the extract 

 coming off from the sawdust, being heavier than the fresh water, fell 

 towards the bottom and became uniformly diffused throughout the 

 vessel. This was the twelfth withdrawal. Black bass fry lived five hours 

 in this water, which was, of course, becoming more poisonous all the 

 time. 



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

 The bag is still floating. The water was changed for the twentieth time 

 at 9 p.m. last evening. At 9 a.m. to-day a black bass fry was immersed 

 in this solution. In two hours it was dead. Some of this solution was 

 evaporated and was found to contain 160 m.gs., or, allowing for the re- 

 sidue after ignition, eighty parts per litre. That is, pine sawdust soaking 

 continuously since June i6th, with the water on it changed twenty times 

 furnished in twelve hours eighty parts per million of poisonous extracts 

 from its wood cells. 



Comparing these figures with those for a saturated solution already 

 given,viz.,i,i6o parts for 1,000 c.c, we see that there has been a continuous 

 withdrawal of poisonous material from the sawdust. The question, 

 therefore, of determining whether any stream is polluted with pine saw- 

 dust or not is largely the question of determining the minimum amount 

 of sawdust extracts which will kill fish eggs, fry, adult fish, and fish food. 

 Needless to say, such determinations would have to be made for every 

 sawmill stream in Canada, and for each separate kind of fish. 



Other Wood Extracts. 



A number of experiments were made with extracts from other 

 woods besides pine and cedar. Norway, or red pine, British Columbia 

 cedar, maple, hemlock, oak, ash, elm were all used, but it was soon dis- 

 covered that the most poisonous extracts were obtained from the pines 

 and cedars. Consequently experiments with the hard woods were soon 

 discontinued. 



From all hard woods, however, the saturated yellowish-brown 

 extract was found to be very poisonous to both adult fish and fish eggs. 



The following experiments give typical results in the case of each 

 of these woods. 



