392 



Fresh Aerated Boiled 



The fishes lived. .23 minutes 81 minutes 150 minutes 



These samples of waste were kept in loosely stoppered bottles 

 for nearly a year and still showed differences of lesser magnitude. 



The fractional distillation of tar yields various different sub- 

 stances. One of these distilled off at 26o°-290°C., which gives heavy 

 constituents only, was supplied by the Department of Chemistry and 

 proved very toxic. 



1000 pts. per million (by volume), not all in sol., killed various fishes in 5-10 min. 



250 '' " '' '' '' }>})!}}? r> }! yy } t If). "A '' 



125 '' '' " '' '' 1 1 T> 1 1 1 ■) !> >j >> !> 25-40 " 



90 " " " " " >> yy y' y> " Lepomishumilis " 40-60 " 



|"0 '' '' '' '' '' }}!>}}}) !) ?} ;> }> 55-60 '' 



Since apparently not more than half of these amounts went into 

 solution and tarry film adhered to the bottle, the heavier parts of the 

 tar are very toxic and remain so for long periods. 



3. TOXICITY OF ILLUMINATING GAS AND CONSTITUENT GAS-MIXTURES. 



As shown by Marsh ('07), illuminating gas is very toxic to fishes. 

 It is difficult to determine how much gas is required to produce fatal 

 results in a sufficiently short time as the constituent gases go into solu- 

 tion with different rapidity and the constituents in a given sample of 

 dissolved gas are difficult to determine, so that no attempt was made 

 to analyze them. The illuminating gas was introduced from an in- 

 verted bottle (U) as shown in figure i. The gas was led into a bottle 

 by displacing water and the bottle stoppered with a two hole rubber 

 stopper wired in place and containing one tube reaching to the bottom 

 and another passing through the cork only. A valve leaking by drops 

 was attached to the short arm and the water thus forced into the bot- 

 tle, drop by drop. The gas was accordingly forced into the cooling 

 and solution coils of the apparatus, much of it going into solution, 

 but a quantity passing through to the mixing bottle and collecting, 

 where it was allowed to escape from time to time. 



A mixture of ethylene 30 cc. per liter, carbon monoxide approxi- 

 mately 6 cc. per liter and sulphur dioxide about 33 cc. per liter killed 

 the standard fish in 15 minutes. 



4. REACTIONS OF FISHES TO WASTE. 



Much of the danger to fishes from pollution of streams, especially 

 where the pollution is local, is determined by the reactions of the fishes 



