BOOK VIIL XVII. 1-4 



bottom to the uppermost part. The pond is either 

 hewn in the rock, which only rarely occurs, or built 

 of plaster on the shore ; but in whatever way it is 2 

 constructed, if it is kept cold by the swirl of water 

 which is constantly flowing in, it ought to contain 

 recesses near the bottom, some of them simple and 

 straight to which the " scaly flocks " " niay retire, 

 others twisted into a spiral and not too wide, in 

 which the lampreys may lurk. Some people, however, 

 hold that lampreys should not be mixed with fishes 

 of another kind, because, if they are seized with 

 madness, which sometimes happens to this sort of fish 

 just as it happens to dogs, they very often pursue 

 their scaly companions and chew them up and devour 

 great numbers of them. If the nature of the ground 3 

 permits, channels should be provided for the water 

 on every side of the fish-pond ; for the old water is 

 more easily carried away if there is an outlet on the 

 side opposite to that from which the wave forces its 

 way in. We are of opinion that these passages, if 

 the lie of the ground is suitable, should be made 

 along the lowest part of the enclosure, so that a 

 plummet placed on the bottom of the pond may 

 show that the level of the sea is seven feet higher ; 

 for this measurement in the depth of the water is 

 fully enough for the fish in the pond, and there is no 

 doubt that, the greater the depth of the sea from 

 which the water comes, the colder it is, and this suits 

 the swimming fishes very well. But if the place 4 

 where we think of constructing the fish-pond is on 

 a level with the surface of the sea, the pond should be 

 excavated to the depth of nine feet, and two feet 

 below the top streams of water should be conducted 

 along small channels, and care must be taken that 



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