Preliminary Considerations. 15 



eggs hatched under unfavourable conditions will 

 never thrive nor do well. 



The means of supply, again, forms a matter of 

 some importance. If the water be derived from 

 waterworks, it will, of course, only be neces- 

 sary to have it laid to the hatching-house, and 

 to see that the pipes are sufficiently large. 

 Hydraulic rams are expensive ; but if one be 

 already on the estate, should it throw plenty 

 of water, it may be used. However, there is 

 always an uncertainty about rams, as the least 

 thing puts them out of order, and it takes some 

 time to induce the machine to work when once 

 stopped. For instance, an eel gets under one of 

 the valves in the night and stops the machine, and 

 has to be removed by unseating the valve ; this 

 empties the pipes, which then become charged 

 with air, and it often takes some hours to force this 

 out, and to obtain a fresh supply of water. A 

 thaw after a sharp frost has almost always a very 

 injurious effect on the action of hydraulic rams. 



