44 FISH HATCHING. 



that from those left to their natural course 

 there ^yould not have been so many fecun- 

 dated eo'o-s from the 310 as ^to have m the 

 breeding-boxes from the forty fish. All 

 these fish "were caught on one ford ^yhere the 

 Almond joins the Tay." 



Then again, we have the reverse of floods 

 — vre have droughts ; and the nests made 

 when the water is liigh become bare and 

 exposed to the air when the water goes 

 down ; either the eggs die from this cause, or 

 else the young when hatched out, having no 

 water, " refuse to exist." 



I have seen a shallow ditch leading out of 

 Ruislip Eeservoir one mass of dead fry of 

 roach, dace, and jack, the water having been 

 let out for the canal. 



Nor must we foro-et mill-wheels. Here is 



