HATCHING FISHES' EGGS IN JAES 181 



involves no cost of maintenance ; when a fall of 

 land is not sufficient for this economical method, 

 power must be brought into play. The best 

 and cheapest pumping machine is a ram. In 

 case the instalment of a ram is not feasible, the 

 next best means of pumping is by a water- 

 wheel. Failing this a pump must be installed 

 with some sort of a heat-engine, unless city 

 water — usually good enough — ^may be used. 



For eggs which require a long period to eye, 

 like whitefish or lake herring, or those which 

 yield to fungus easily, like wall-eyed pike, uni- 

 formly clean water is important. For shad 

 eggs it is not of such great concern, although 

 desirable, and for yellow perch it is a matter 

 of little or no moment, except that it makes 

 more work. 



Batteries. — Two distinct tj^es of batteries 

 are in operation, one very complicated in con- 

 struction and the other almost the perfection 

 of simplicity. 



The first has both supply and waste troughs, one 

 system set lengthwise and the other crosswise. The 

 latter are arranged like a flight of steps, with an 

 overflow in the centre, for the purpose of enabling 



