METHODS OF CONSTRUCTING BREAKWATERS. 237 



Cranes, or Over-end Setting Machines, are used for setting 

 blocks and building masonry, also for putting in mass-work and 

 bag-work, and depositing blocks pell-mell in wave-breakers. 



In constructing the breakwater at Leixoes, in Portugal, an ex- 

 ceptionally large " Titan," with a maximum working radius of 

 144 feet, was used for depositing rubble in the mound ahead of the 

 built work ; but this is unusual, and in many cases would not be a 

 desirable system to adopt. 



Staging. Amongst the many breakwaters which have been 

 constructed from staging, those at Holy head, Portland, Dover, 

 Table Bay, Ymuiden, Alderney (in part), Hartlepool, and the 

 south breakwater at Aberdeen, may be cited as examples. 



The facilities afforded by staging for depositing rubble to 

 form the mounds of breakwaters are very great. This fact was 

 fully recognized during the construction of the Portland break- 

 water, insomuch that after the completion of its landward 

 section, which had a length of about 1700 feet, and which would 

 have afforded excellent shelter for barges, had it been desired 

 to use them, the same system of depositing from a stage was 

 adhered to for the outer isolated breakwater, which was 

 6400 feet in length, and this notwithstanding that an opening 

 between the end of the shore breakwater and the commencement 

 of the outer breakwater had to be left. Although this opening 

 was only 400 feet in width, it necessitated the construction of a 

 bridge, or extra strong length of staging, measuring about 1000 

 feet. This may, therefore, be viewed as a parallel case to con- 

 structing, by means of staging, an isolated breakwater 1000 feet 

 distant from the shore. 



By the use of staging in constructing rubble-mound break- 

 waters, work may be carried on uninterruptedly in almost all 

 weathers, thus giving constant employment to all those engaged 

 upon it, and effecting a large saving in cost. 



If stone cannot be readily disposed of, the quarry soon 

 becomes blocked, and plant, including that used in conveying 

 the stone from the quarry to the breakwater, lies idle, whilst the 

 return for wages is practically nil. 



Another advantage possessed by staging is the facilities 

 which it affords for ascertaining the level and line of the rubble 

 as the formation of the mound proceeds, and also for depositing 

 rubble of various classes on defined lines, if such should be 



