H4 HARBOUR CONSTRUCTION. 



the great advance which has been made in mechanical appliances 

 for dealing with heavy loads at long radii, has quite revolu- 

 tionized the system of breakwater construction, by rendering 

 it possible to build heavy blocks on shore, and set them in place 

 after they have become hard enough to resist the action of the 

 sea. Large bags, containing concrete in a soft state, can also 

 now be deposited with the greatest ease. 



Hydraulic Lime in Sea-works. English engineers seem to 

 have little faith in lime for sea-works, seeing that, almost 

 without exception, they now employ Portland cement. French, 

 Italian, and some other engineers, on the other hand, still use 

 lime rendered hydraulic by the addition of substances in which 

 silicate of alumina predominates, such as puzzuolana. 



As bearing upon this subject, I may mention the following 

 facts which have come under my notice. 



The masonry of the superstructure of the Holyhead break- 

 water was set in lias lime mortar, with which, in some portions 

 of the work, puzzuolana was incorporated. 



In course of time the sea removed nearly all the mortar from 

 the joints and beds of the masonry for a considerable distance 

 in from the face of the work. The seaward face, as it is natural 

 to suppose, was affected most ; nevertheless, it was necessary to 

 rake out the joints on all the exposed surfaces of the work 

 including those on the harbour side, which were exposed to the 

 small waves coming across the bay and to fill and repoint them 

 with Portland cement mortar. 



On the sea face of the superstructure holes of considerable 

 dimensions were formed in the masonry, through stones be- 

 coming loosened by the abstraction of the mortar. These were 

 discovered and stopped in time, otherwise they would, no doubt, 

 soon have increased in size and endangered the work. 



Lime mortar was therefore a failure in this case, and it was 

 noticed that the addition of puzzuolana, so far from improving it, 

 appeared to have a positively injurious effect. 



Notwithstanding this, it must be admitted that French and 

 Italian engineers have beon more successful than ourselves in 

 the use of lime in sea-works, seeing that it has been largely 

 employed by them in most of the marine works along the shores 

 of the Mediterranean, and is, indeed, still being extensively used. 1 



1 The exceptionally good quality of Mediterranean limes conduces, no doubt, in 

 a great measure, to the success which attends their use. 



