1902-3.] Sawdust and Fish Life. 457 



expect to find that bark solutions were very destructive to fish life and 

 fish food. The very opposite was found to be the case. Compared 

 with the wood extracts, the bark solutions were comparatively harmless. 

 Even tan bark, much execrated by fishermen and anglers alike, was not 

 so poisonous as one might expect, but the experiments must speak for 

 themselves. 



White Pine Bark. 



Only 1 1 per cent, of sawdust from this bark sank in ten minutes. 

 A black bass fry seemed perfectly unharmed after being three hours in a 

 solution of this bark that had been forming for twenty-two hours (one 

 gram in seventy-five c.c. tap water). The animal was then returned to 

 the fresh water aquarium. 



This same bark, after soaking two weeks, gave a solution that killed 

 solely by suffocation. This was quite apparent from the fact that two 

 minnows when placed in this water (freely aerated) lived for fwenty-four 

 hours and were then liberated. When the solution was unaerated the 

 minnows died in an hour or two. Pouring the solution several times 

 from one vessel to another areated it sufficiently to enable two minnows 

 to live three days in it without apparent harm. 



After standing six weeks a scum formed on the surface. This was 

 removed and the solution aerated by pouring it several times from one 

 vessel to another. A minnow now lived in it for two days and was 

 liberated, apparently as well as ever. 



Hemlock Bark. 



A solution made by soaking one gram of this sawdust bark for 

 fifteen hours in 100 c.c. of tap water killed a minnow in six minutes. 

 After soaking for two weeks this water killed a minnow in one hour, 

 even when thoroughly aerated. But these were very strong solutions 

 compared with the ones obtained from wood. 



Cedar Bark. 



Only 5 per cent, sank in fifteen hours. In two days it had all sunk 

 excepting about i per cent. A i per cent, solution (one gram in lOO 

 c.c.) made in fifteen hours, rendered a minnow moribund in fourteen 

 minutes. Here again the solution was a very strong one compared with 

 those obtained from wood sawdust and used in the experiments previ- 

 ously described. 



