SALMONOIDS AND TUBBINES. 251 



turbine-pit a single living Trout was in it, whilst in the turbine- 

 pit a considerable number of Trout (twenty to thirty) remained, 

 partly from the previous experiment and partly pertaining to 

 this. No dead fish was seen. 



(VIII.) In this instance a 48-in. Leffell turbine, having ninety 

 revolutions per minute, was used. The pit of the turbine was 

 8 ft. square by 9 ft. deep. Sixty-two Perch, about 4|- in. to 

 5 in. long, were placed in the box formerly described, and 

 released close to the edge of the moving turbine at 3.45 p.m. 

 In a minute and a half one or two passed into the net at the 

 tail-race, and in four minutes another struck the ladder at the 

 net. Many leaves, weeds, and other debris were carried into the 

 tail-race where the net was placed, about 25 ft. from the turbine. 

 In eleven to twelve minutes the revolutions of the turbine were 

 slowed to fewer than eighty, and again increased in velocity. 

 At 4.12 p.m. they were seventy per minute. By clearing the 

 iron guards, between each of which there was a space of Ij in., 

 the flow of water was increased, and the number of revolutions 

 was eighty-six. The machinery was stopped in forty minutes. 

 In the net stretched across the tail-race were thirty- eight Perch 

 in fair condition, which were placed in water for further experi- 

 ments. All these had passed unscathed through the turbine. 

 No dead or wounded Perch could be found, for the turbine-pit 

 was thoroughly searched by Mr. Armitstead, and no trace of a 

 fish was found in it. These fishes (Perch) are, compared 

 with the agile Trout and Smolts, stiff and rather thick fishes ; 

 yet, so far as could be ascertained, the mortality was trifling. A 

 considerable number probably lay in the tail-race above the net, 

 or had escaped by chinks at the side. 



(IX,) Into the same turbine-pit, at 5.15 p.m., one hundred 

 and thirteen mixed Trout were placed by aid of the box close to 

 the apertures of the turbine in action. In five minutes the 

 revolutions were seventy per minute, in four minutes after 

 eighty revolutions ; at 5.25, seventy revolutions, and in three 

 minutes thereafter eighty-six revolutions. These irregularities 

 were due partly to changing gear, and partly to the clearing of 

 the iron guards of the head-race. The machinery was stopped 

 in twenty-nine minutes. Out of the net came three Perch which 

 had passed through the turbine in the previous experiment, and 



