THE FISHERIES. 39 



The Board of the Drogheda District suggests an 

 opening of three inches upon a surface of two feet 

 six inches on the crest of the weir, to be closed when 

 necessary ; but we are of opinion that three inches 

 of water upon this extent of surface, no matter how 

 adapted or apphed, would not form a sufficient 

 "lead," and would be, therefore, useless; it would 

 swamp in flood-time, and in low water would not act 

 at all. We conceive that the minimum will be a vo- 

 lume of three inches upon a surface of sixteen or 

 eighteen feet, collected in the centre of an inclined 

 plane by its concave surface, in the way we shall 

 presently describe. The Ballina Board propose, 

 that below the mill-weir, two other weirs should be 

 constructed in a descending scale, with openings in 

 the centre of each weir. This would, undoubtedly, 

 form a perfect salmon-pass, but the great expense it 

 would occasion puts it entirely liors de combat. 

 Other devices have been suggested by individuals, 

 equally efficacious but equally impracticable, either 

 by reason of the expense, or of interference with the 

 water-power of the mill, which latter is a fatal ob- 

 jection to any plan, whenever it arises. 



We shall, therefore, proceed to give our own no- 

 tions upon this knotty point, and suggest how those 

 devices may be best constructed. The problem to 

 be solved is somewhat difficult of explanation, but we 

 must discuss it, since many, and well-founded are the 

 complaints that nothing has yet been done in this 

 department. 



