OUR RIVER HARVESTS. 273 



has erected and still maintains the greater part at his 

 own expense. This, although on a small ^ale, is 

 marvellously successful, and is capable of producing 

 nearly one hundred thousand fish annually. 



The process is as follows : 



Within a moderately-sized green-house have been 

 erected a series of troughs formed of slate, and 

 arranged one above the other like so many stairs. Each 

 trough is three feet in length, seven inches in width, 

 and five in depth. It is found, however, that the 

 depth need not exceed four inches. In these troughs 

 is placed a layer of moderately fine gravel, about two 

 inches in depth, and larger stones are stuck into the 

 gravel at intervals of an inch or two. The gravel and 

 stones have been previously boiled and washed, in order 

 to destroy all traces of decaying animal matter which 

 might taint the water, all aquatic creatures which 

 might injure the eggs or fry, and all confervoid 

 growths which might choke up the stream and inter- 

 fere with the wellbeing of the young fishes. 



Above these troughs is placed a large tank holding 

 about two hundred gallons of water, which is conducted 

 to the upper trough by means of a pipe and stopcock. 

 At alternate ends of each trough is placed a short pipe, 

 which conveys the water from one to the other, and in 

 consequence of their alternate arrangement compels the 

 water to traverse the entire surface of the gravel. 



The eggs are carefully laid upon the gravel so as to 

 lodge in its interstices, each trough containing three 



T 



