METHODS OF CONSTRUCTING BREAKWATERS. 251 



An excellent machine of the radial type, capable of dealing 

 with working loads of 50 tons at a radius of 109 feet, is now in 

 use at the breakwater which is being constructed under the 

 direction of Mr. H. H. Wake, M. Inst. C.E., at the mouth of the 

 River Wear. 



Machines of the " all-round" type are, as their name indicates, 

 capable of revolving around the entire circle. Ordinary long jib 

 travelling-cranes are of this type, and for constructing small piers 

 they are very efficient and comparatively inexpensive. 



In machines of the larger class, the movable arm is usually 



I I I I I I I I III 



SCALE 



10 15 20 25 ' 30 FEET 



FIG. 66. Block-setting machine as used at MormugSo. 1 



made horizontal, being either formed of rigid cantilever girders, 

 or of lighter longitudinals supported at two or three points along 

 their length by tie-rods attached to, and extending from, the 

 top of a central rigid post or frame. Type-sketches of these 

 machines will be found in Figs. 67-69, p. 252. 



In machines of this class, the movable arm usually revolves 

 upon a number of rollers fixed in a frame, forming what is 

 technically known as a " live ring," and the design, generally, 

 very much resembles that of a swing bridge mounted upon an 

 under-carriage. The "jenny," as in the case of radial machines, 

 travels upon the top of the movable arm, and has no transverse 



1 Min. Proc. Inst. C.E., vol. xcvii. 



