264 



HARBOUR CONSTRUCTION. 



In the event of the work being constructed over-end by a 

 setting machine which could not command a sufficient distance 

 ahead to deal with it in this manner, the situation might prove 

 awkward, and some other means of putting in the work would 

 have to be devised. 



In dealing with such cases, as indeed with irregular rock 

 foundations generally, staging possesses great advantages as 

 compared with the over-end system of construction. 



It often happens that several descriptions of work might be 

 in progress at the same time, as, for example 



(a) Removing loose gravel, boulders, etc. 



(6) Boring and blasting the rock in various positions, and 

 removing the debris. 



(c) Putting in bag-work or mass-concrete, and levelling 



foundations. 



(d) Setting blocks, and so forth. 



It is obvious that these several sections of the work not only 

 might, but ought to be in progress at the same time, and this 

 can with ease be arranged where staging is used. The case is, 

 however, far otherwise where the over-end system is adopted, 

 inasmuch as the setting-machine is wholly occupied when 

 engaged on any one of the sections of work above named, its 

 whole time being often taken up with work which could be 

 better performed by a handy 4- or 5 -ton crane or winch running 

 upon a stage. 



The advantages which staging possesses, as compared with 



