Thomas. — Effects of Certain Oils Upon Brook Trout 135 



short space of time. It is believed that only the tars and oils 

 which are of a toxic nature chemically would affect the fish when 

 washed into streams by rains. 



The problem of creosotes is chiefly to be met with where 

 wood that is to be submerged in water, is treated with them; or 

 where nets are so cured. It is thought that by allowing the wood 

 to dry for a sufficient period before placing in water will greatly 

 prevent detrimental results. 



SUMMARY. 



Products from gas works, and coal-tars containing substances 

 somewhat soluble in water, were found to be exceedingly toxic 

 to the fish. This is probably due to the fact that they contain 

 some soluble substances, such as phenols and like compounds. 



Crude oils and asphalts caused no toxic effect except that the 

 crude oil would emulsify upon continued agitation and, if in the 

 water in large proportions, finally coated the gill membranes 

 of the fish thus inhibiting respiration. This is purely a mechanical 

 effect, such as is unlikely to occur in streams or ponds. 



The concentrated waste sulphite liquor, as obtained, did not 

 kill the fish when added to the water in only small amounts, yet 

 in these dilute solutions the fish would at times show signs of 

 distress and were killed by higher concentrations. The results 

 obtained tend to show that the presence of this material in natural 

 water would cause the fish to seek an unpolluted locality. 



Creosotes when added to water proved to be highly toxic. 

 Aeration somewhat diminished the toxicity probably by the 

 oxidation of the products themselves. In all but two cases wood 

 treated with creosotes and then dried did not affect the fish, and 

 in those two cases the toxicity has been greatly reduced by the 

 exposure to air. 



