74 IMPROVED FISHERY HARBOUR ACCOMMODATION 



determined these centres from which the waves expand, 

 and which, he says, " appear to be situated not far from the 

 middle of the entrance." 



The writer will now proceed to mention the devices 

 adduced by Mr. Stevenson, as carried out or recommended 

 by several engineers, for the reduction of waves in close 

 harbours, after which he will venture to make some sugges- 

 tions of his own for the purpose of bringing about the same 

 result. 



SIDE CHANNELS FOR REDUCING WAVES. 



"At the harbour of West Hartlepool an ingenious and 

 novel device for reducing the height of the waves has been 

 carried out by Mr. R. Ward Jackson and Mr. Casebourne. 

 Interior expansions have been made to communicate with 

 narrow canals, running landwards, and which ultimately 

 join the sea outside the harbour. The portion of the wave 

 which has been detached by spreading into the lateral 

 channels is thus conducted entirely out of the harbour 

 into the open sea." 



CELLULAR STRUCTURE FOR REDUCING WAVES. 



" There are many situations so narrow and confined as not 

 to admit of the formation of lateral expansions either of 

 the usual kind or of that adopted at Hartlepool ; in such 

 situations some reduction may be effected by converting 

 the upper portion of the quay-walls at and near the 

 entrance into a series of chambers, separated from each 

 other by vertical diaphragms, so as to smooth the water by 

 forming numerous stops. This cellular structure, in some 

 respects similar to what is called in France ' claire voiej 

 might be cheaply constructed of vertical partitions of 



