Thomas. — Effects of Certain Oils Upon Brook Trout 137 



been poured in within a few miles up the river. The only explanation has 

 been that the fish have been turned away, because they have appeared very 

 universally in neighboring rivers. Instead of going into their own river, 

 they were turned away by the flavor of the water, as it were. 



Mr. Thomas: I am very glad indeed to hear what Doctor Prince has 

 to say. Having investigated nearly a dozen cases in the state of Virginia 

 during the past year, I received reports, each time before I made the inves- 

 tigation, that thousands of fish had been killed by a certain pollution, but 

 only in one instance did I find any evidence of fish having been killed. It 

 seems they are simply driven away, and seek other localities. Fish above 

 the source of pollution are as numerous as ever, and some miles below the 

 source of pollution fish begin to show up, according to the amount of pollu- 

 tion which is poured into the water, and they increase as you go further down 

 stream. In only one case have I noticed recently where any number of fish 

 were killed, and that was from a furnace and iron works where the fuel 

 gases were washed before being used as fuel. These gases contained prussic 

 acid, and I found as much as thirty parts per minim of prussic acid in the 

 water which was sent into the stream. Of course that did kill the fish, and 

 very quickly, inside of forty-eight hours after the furnace was started. We 

 have had no fish in that stream since, but are taking every step to prevent 

 any more prussic acid being poured into the water; but that is the only 

 instance that has come to my attention where any great number of fish 

 have been actually killed by pollution. 



Dr. R. C. Osburn, of Ohio State University: I wish to ask Mr. Thomas 

 if, in the course of his experiments, he has noticed any difference in the 

 toxic effect of these substances at different temperatures. It occurred to 

 me when Dr. Prince was speaking that possibly the lack of effect, or slight 

 effect, which he noticed might be due to the lower temperature of the water 

 in Canada, as we know that many substances have less effect at lower 

 temperatures. 



Mr. Thomas: I have not sufficient data to publish it, but my investiga- 

 tions showed that with higher temperatures, tars and creosotes affected 

 the fish much more readily. I am almost forced to believe that it is due to 

 the solubility of these substances in the water at higher temperatures. With 

 oils undoubtedly the temperature has considerable to do with toxicity. 

 I tried to run these experiments with a variation of five or ten degrees. I 

 have not had an opportunity to continue the study with reference to tem- 

 perature changes, but preliminary experiments show that undoubtedly the 

 temperature is a great factor in producing a toxic effect. In cases of ordi- 

 nary pollution I do not believe that the temperature would have very much 

 effect. 



Mr. W. E. Barber, of Wisconsin: It seems that we have a proper 

 diagnosis of the disease, and now what we want is an absolute remedy for 

 this pollution. We have discovered that where the deposits from the pea 

 canneries enter our rivers and streams the fish are killed. The paper waste 

 seems to drive them away. We do not find dead fish, but there are no fish 



