FOR GREAT BRITAIN AND IRELAND. 75 



timber. The action of the cells consists in abstracting 

 from the upper portion of the wave a small part of the 

 water, and retaining it momentarily until the crest has 

 passed the mouth of the cell, when the water so retained is 

 again discharged into the harbour on the back of the wave 

 from which it had been abstracted." 



"Although the openings were of small width, still, it 

 the entrance passage were of some length, a considerable 

 reduction would be produced by this repeated process of 

 separation and detention. The equalising tendency of the 

 stops may to some extent be judged of by noticing the 

 action of vertical fenders on a passing wave." 



" On a somewhat similar principle the waves are some- 

 times reduced by making a portion of the outer piers 

 of open timber- work, which allows the wave to burst 

 through it." 



STILLING BASIN. 



" As before mentioned, it is in some cases essential that 

 there be either a considerable internal area, or else a 

 separate basin opposite the entrance, for the waves to 

 destroy or spend themselves. Such a basin should, if 

 possible, inclose a portion of the original shore for the 

 waves to break upon, and when circumstances preclude 

 this, there should be a flat talus of at least 3 or 4 to I, as 

 recommended by Mr. Bremner of Wick. Mr. Scott Russell 

 has found that talus walls of i to I, or steeper, will not 

 allow the waves to break fully, but will reflect them in 

 such a manner as might in some instances make the 

 entrance difficult or even dangerous of access, and the 

 berthage within unsafe ; and I can corroborate this from 

 personal observation. Instances are not wanting of 

 harbours being materially injured by the erection of a 



