FOR PLEASURE AND PROFIT. 65 



run dry, or the course of the stream again diverted, and the 

 faulty work put into thorough repair. But the go'lden rule is 

 to make assurance doubly sure in the first pia,ce ; for it must 

 not be forgoltew that where disaster occurs not only is work- 

 manship destroyed, but, in mahy cases, the stock of fish is lost 

 also, only be regained at considerable expense, and certainly 

 at great loss of time. A free flow of water through a screen 

 is a sine qua non. Hence it follows that where much debris 

 comes down a river a pair of screens (one much coarser than 



FRY ENCLOSURES FORMED OFF A BROOK. 



the other) is an advantage. So far as the material from which 

 they should be made is concerned, a* great deal depends upon 

 the size of the screen. Where a somewhat broad river is 

 screened off into sections, upright bars firmly riveted into 

 stout iron frames is the approved method ? or a stout frame- 

 work of wood may be covered by an approved size of galvanized 

 upright wire screens, as shown in the photograph of the Itchen 

 river screen. But when the work is of less importance in 

 size, stout, perforated zinc is generally used. The objection 

 to perforated zinc is the need of frequent renewal, but this, 

 after all, is merely a minor matter, and the expense is not 



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