i82 THE SEA-TROUT 



and not liable to the slightest risk of interruption, for any cessation of 

 the flow at a critical juncture would be disastrous. For these reasons 

 the water supply available will determine the site. 



At Luss, where a connection has been permitted with the gravitation 

 water supply, delivery is made by a ^ in. lead pipe, but the head of 

 water in each case will determine the diameter of the pipe necessary 

 to deliver the quantity of water requisite. This, roughly speaking, must 

 be sufficient to give to each hatching box a complete interchange of 

 water every three minutes, but I shall have more to say upon this point 

 later. 



In some convenient stream a natural pool must be looked for 

 giving a fall of at least 30 ft. to the proposed hatchery. If, however, 

 no such pool can be found, a small dam can easily and cheaply be 

 engineered to form one. In the pool so found, or formed, a small 

 covered chamber should be constructed, guarded at the intake by an 

 iron grating to exclude flotsam. From within this chamber the main 

 water pipe, further protected by a rose, will be led to the hatchery. If 

 the water can first be filtered through an outer chamber of gravel, 

 additional security will be given against danger from the deposited 

 sediment of " spate " water. The pipe will terminate within the 

 hatchery itself. 



This, then, is a simple wooden structure, 20 ft. long by 17 ft. broad. 

 The back wall is 7 ft. and the front wall 1 1 ft. 4 in. in height, giving 

 the lean-to roof, which is covered with patent roofing felt, sufficient 

 slope from front to rear to throw off the rainfall. The whole structure 

 is thoroughly tarred over. As direct sunlight, or indeed a strong light, 

 is detrimental to the ova, the house faces away from the south, and this 

 front wall alone is pierced with door and windows. Of the latter, one 

 is over the door and one on each side, and all three are obscured by 

 green cloth roller blinds. 



The walls, of ordinary white pine, are built double, and the spaces 



