Ant erica II Fisheries Society. 199 



of intake, all ^vill Ix' well. If the suction pipe is of wood, very 

 slight breaks or a general porosity may develop as the wood de- 

 cays, a condition which may not be noticed since air leaks in 

 instead of water leaking out. The first entrance of air will prob- 

 ably be small in amount and make only moderate trouble with 

 the stock of fishes, a trouble which would not readily refer itself 

 to its real cause. Very slowly and gradually these leaks increasa 

 and the mortality becomes gradually and insidiously more seri- 

 ous, until the water kills all fishes soon after they are placed 

 within it. This insidious progress has aided in oljscuring the 

 real nature of the mortality. 



DISCUSSION. 



Mr. Atkins : I would like to inquire whether there is any 

 ready means of measuring the amount of air in water and ascer- 

 taining by any sort of observation, so that we can know when 

 there is an excess. 



Mr. Marsh: A chemical determination will show, but it is 

 rather lengthy .and involved. I do not know any very ready 

 means except this. A'ou can take two glass stoppered bottles, 

 where the stopper fits perfectly, and fill one absolutely full of 

 some ordinary water, and insert the stopper so that there are no 

 bubbles whatever, letting it stand until any bubbles that may he 

 in it are dissipated, insert the stopper so that after it is in no 

 bubbles will be seen ; then take in the same way a sample of sus- 

 pected water and put them together where it is warmer, or put 

 them in a dish of warm water and let them come up to the same 

 temperature. Then in the case of the one that has the most air 

 there Avill separate from it the' greater amount of air ; you can 

 see which buliljle is the larger. A^ou can get a rough idea that 

 way. 



Mr. Atkins : Perhaps that is close enough for practical use. 



^Ix. :\rarsh : I would try it. If from such a l)ottle tlun-e sep- 

 arated no more gas than from a bottle of water I knew contained 

 no excess, the inference could easily be drawn that there was no 

 excess in the suspected water. If the bubl)l('s were larger it 

 might merely be better aerated. 



General Bryant: Was this water sea water? 



Mr. Marsh: A\^s, sir. 



