AND PEOTECTION OF AGRICULTURAL LAND. 63 



and after storms any of the rubble that has been drawn down by 

 the waves should be at once replaced with additional rubble, till 

 the whole has acquired stability. 



The accompanying cut, fig. 8, shows the nature of this work 

 as actually executed by Messrs D. and T. Stevenson, on a pretty 

 extensive scale, to protect carse lands in exposed situations, and 

 I refer to it as a style of defence, varied, of course, to suit par- 

 ticular exposures and localities, which may very generally be 

 successfully applied where stone can be easily procured. 



In some places, such as the mouth of the Humber, the inroads 

 of the sea have been successfully resisted by occasional groins 

 run out from the beach ; and it may, in many cases, be prudent, 

 as a first measure, to ascertain the effect of groins, as -in the 

 event of their proving successful the expense of any continuous 

 line of defence may be saved. In so far as my own experience 

 goes, however, isolated groins do not generally prove a satisfac- 

 tory defence, and have to be supplemented by longitudinal work 

 of some description. I may, as exemplified in several places 

 where groins have been tried on the shingle beaches of the 

 southern shores of England, refer to one instance of this coming 

 within my own experience at the Bristol Channel, already 

 noticed, where jetties run out at right angles to the high-water 

 line had long been tried without good result. I found that in 

 heavy seas the waves were led along the jetties, and struck 

 with great force in the corner where they joined the beach at 

 high-water mark. I further found that the shingle of which the 

 beach is composed was heaped up on the western sides of the 

 groins by prevailing westerly winds, while it was heaped up on 

 the eastern side of the groins by winds which had prevailed from 



