VARIOUS TYPES OF BREAKWATERS. 



191 



concrete to be used in this class of work are 1 part of Portland 

 cement to 4 or 5 parts of sand and shingle or broken stone. 

 The proportion of sand relatively to the stone or shingle should 

 be rather more than is used for work above water, and the 

 concrete should be mixed rather wetter. The shingle should 

 not be too coarse, and the stone should be broken extra small. 



Fig. 34 illustrates a frame for depositing concrete bags which 

 I designed with the 

 view of enabling 

 divers to make closer 

 and more regular 

 work than is possible 

 when bags are drop- 

 ped out of boxes in 

 the ordinary way. 



Bags for use with 

 these frames are pro- 

 vided with bands or 

 girths, terminating in 

 tabs, in each of which 

 an eyelet - hole is 

 worked. The bags, 

 when being filled, are 

 placed in rectangular 

 boxes which have 

 movable sides. When 

 a bag is full it is sewn 

 up, and the frame 

 is placed upon it. 

 The tabs are then 

 hitched upon the side 

 hooks, and the sides 

 of the box released by 

 knocking up a catch, 

 the bag being then ready for lifting and placing. The bags 

 retain, in a somewhat remarkable manner, their rectangular 

 form, even when they contain very soft concrete ; and divers are 

 able to make very close work with bags deposited by means of 

 frames in this manner. After a bag has been placed in position 

 the tabs are unhooked, and the frame is thus released. The tabs, 

 being of no further use, are usually cut off. 



FIG. 34. Frame for depositing bags of concrete 







