72 IMPROVED FISHERY HARBOUR ACCOMMODATION 



indeed, to find that a single observation or experiment of 

 any kind has been made upon the subject, and yet the 

 whole benefits which are expected to result from the 

 erection of our great national breakwaters depend entirely 

 upon this reduction of the waves'' It is scarcely possible 

 to speak more strongly than this, and on account of its 

 very great importance the writer hopes he may be 

 pardoned for again quoting the three striking paragraphs 

 from Mr. Stevenson (pp. 118, 119, and 120) which he has 

 already quoted at page 44 of this essay : 



" When a wave encounters an obstacle such as a break- 

 water, if we suppose the portion which strikes it to be 

 annihilated by the impact, or to be reflected seawards, the 

 portion which is neither destroyed nor interrupted will 

 spread laterally behind the breakwater. 



" When the waves are deflected by a pier with a free 

 end, and run along its inner side, the reduction which they 

 suffer will be due to the distance passed over, and to the 

 angle of deviation produced by the pier. Though far 

 from placing full reliance on so slender a stock of facts 

 as I am in possession of, and which were partly the 

 result of observations at sea, and of experiments made 

 in a brewer's cooling tank about four or five inches 

 deep, I may state that an unbroken wave, after being 

 deflected, was found to decrease in height directly as 

 the distance traversed, and as the square root of the angle 

 of deflection." 



"In the subjoined table are given the heights observed at 

 the harbour of Latheron wheel. These observations were 

 made at the outer kants of the pier of Latheronwheel, 

 which is single, with a free end, and which acts on the 

 waves in a different manner from a harbour which forms an 

 inclosed area, to which I shall next refer." 



