ATKINS ON FISII-WAYS. 605 



trench or in a natural crevice or ravine, the velocity of its flow being 

 moderated by the uneven ness of the bottom and sides, by turns in its 

 direction, or by rude walls of stone, crossing it at convenient points. 

 It commonly assumes the form of a series of pools, gently flosving or 

 eddying, connected by short runs of swift water. In operation, it is 

 when well located, very successful, and being at the same time cheap, 

 is perhaps to be preferred to any other form, where the facilities exist 

 for its construction, and there is no special reason to grudge the extra 

 volume of water that it requires over the more artificial kinds. A good 

 many fish-ways of this form have been in use in -New England, In Mas- 

 sachusetts it has received the name of "Cape Cod fish- way." lu Maine 

 the most notable is at Damariscotta Falls. Damariscotta River is fre- 

 quented by alewives, affording no suitable breeding-grounds for salmon 

 or shad. Tradition says that in its natural state not even alewives en- 

 tered it in any greater numbers than might be supposed to straggle in 

 from the neighboring Pemaquid river. They could not surmount the fall, 

 which is about fifty feet high, rushing down over a rugged ledge. About 

 1806 the inhabitants builc a fish-way, consisting of 20 or 30 pools, in a 

 crevice of the ledge. The alewives rapidly increased, and have yielded 

 large annual returns down to the present time. A few years since the 

 catch was estimated at 1,200,000, which was said to be considerably below 

 the former yield. There are several places in this fish-way that are more 

 difficult for the fish to ascend than any Foster fish-way that I ever saw, 

 yet it seems to meet the wants of the alewives. 



At Brooksville, Me., there is a trench-fish- way around a dam 18 feet 

 high, which has a pretty steep grade, without pools or considerable 

 bends, yet it is quite effective. Alewives are the only fish ascending it, 

 and they accomplish the ascent without difficulty. 



3. — OBLIQUE aROOVE. 



The single oblique groove leading in a straight line down the face of a 

 dam from its apex to the water below has been tried in the British 

 islands and found utterly useless. Its faults are thus described by Mr. 

 Samuel XJ. Roberts, of Gal way, Ireland: 



" The velocity of the water which enters the groove at the apex of the 

 weir increases in its descent down the inclined plane of the groove, its 

 depth becomes proportionately diminished, and it is utterly impossible 

 that any salmon caii pass up it. It is true that when water is flowing 

 over the apex of the weir, additional water will be gathered in the 

 groove, where it is formed diagonally across the apron of the weir ; but 

 this water enters the groove at 07ie side only, and the fish is compelled 

 to swim against the current diagonally, which is unnatural. Any large 

 quantity of water discharged over the apex of the weir will sweep fish 

 out of the groove; while in dry weather, the thin, rapid stream of water 

 on the lower portion of the groove will render it impossible for any fish 

 to ascend." 



