898 BULLETIN OF THE BUREAU OF FISHERIES. 



markedly so, while samples carried in glass containers had no toxic quality. 

 No toxicity was imparted to Potomac water by repeated and long-continued 

 trials in such cans. The toxic element in the water was not identified, but it 

 is of interest to find that it was destroyed or neutralized by some very simple 

 means. Boiling made the water harmless, and heating to 75° C. greatly reduced 

 the poisonous elTect. It was also corrected in large part, sometimes almost 

 completely, by the addition of a portion of either sea water, common salt, cal- 

 cium sulphate, sodium carbonate, residue from the evaporation of Potomac 

 water, or ordinary earth. 



Water brought in fish cans from Newport News, Va., had a similar selective 

 toxicity and was corrected by most of the agents mentioned above and also by 

 the presence of fish in the water, especially by the dead bodies. Thus a sample 

 of this water by standing with the bodies of the fry it had killed became less 

 able to kill other fry of the same species. Shaking and soaking with bone black 

 diminished the toxicity somewhat. These experiments suggest that for aqua- 

 rium exhibits on close circulation or for the temporary holding of fish in standing 

 water, water which it is dangerous or impossible to use may be made fit for 

 fishes by dissolving in it some of the cheap and easily procurable substances 

 mentioned. 



ABNORMAL GAS CONTENT. 



DISSOLVED AIR CONTENT OF WATER FROM A DRIVEN WELL. 



This well was driven in May, 1906, and is 83 feet 10 inches deep. It passes 

 for most of the distance through clays, which include two strata of water- 

 bearing gravel and sand between the 34 and 52 foot levels, and finally takes 

 water from fine sand and coarse sand and gravel beyond a depth of So feet. A 

 6-inch casing reaches the whole depth of the well and contains a 4-inch pipe 

 through which the water is pumped. The casing is perforated for several feet 

 near the 50- foot level, so that the water-bearing gravel at this level contributes 

 to the supply of water. 



The water level in the well stands about 21 feet below the surface of the 

 ground. The electric pump installed was able to lower the level to about 28 

 feet, where it remained constant. The pump as ordinarily run delivered 24 

 gallons per minute, but could be made to deliver 32 gallons per minute. The 

 temperature of the water was about 15° C. (60° F.). 



It was intended that the water be used in the trout aquariums during the 

 summer in order to avoid the expense of refrigerating Potomac water. On 

 April II, 1907, the water was turned into an aquarium containing trout. They 

 soon showed marked distress and the water was then shut off'. The next day 

 the pump was started again and by delivering part of the flow into a glass jar 



