188 A TREATISE ON DREDGES AND DREDGING 



shapes and sizes to satisfy local conditions, but generally they 

 consist of sections of pipes bolted together and supported by floats 

 of any design. The various sections of pipes are joined together in 

 some way so as to permit the whole line to adjust itself to tides, 

 currents and other circumstances. 



The following description, taken from Engineering, will serve 

 to illustrate the method of conveying the materials from dredges 

 to land by means of a pipe line. It was used in connection with the 

 hydraulic dredge ft J. Israel Tarte" designed by Mr. W. Robinson for 

 deepening the channel through Lake St. Peter in the River St. 

 Lawrence. 



The form of pipe line adopted is that of a central conduit 36 

 in. in diameter, carried by two cylindrical pontoons or air chambers 

 42 in. diameter, the three being bound together by truss-frames 

 clamped upon them as shown in Fig. 60, Cut A. In this way no 

 bolts or rivets are put into the air chambers, and they may be readily 

 taken apart. 



The pipes were made up in 100-ft. sections, and four sections 

 of 50 ft. were made with the idea of putting them in that part of 

 the pipe where greater flexibility was required. It was found, how- 

 ever, that these 50-ft. pipes did not stand the sea as well as the 100- 

 ft. sections and that, moreover, sufficient flexibility could be had 

 without them. They were accordingly joined together and con- 

 verted into 100-ft. sections. 



The joints connecting the 100-ft. sections were at first made 

 by uniting them with a forged-steel pin connection over the rubber 

 sleeve, thus relieving the rubber sleeve of all strain due to tension 

 of the pipe and permitting the required angular movement. These 

 joints were not strong enough, and were found to be too rigid in 

 wave-action and caused heavy strains to be set up, which broke 

 some of the joints. They were temporarily repaired for the first 

 season, and during the winter 1902-03 new joints of special con- 

 struction were devised by Mr. Robinson on the ball-and-socket plan 

 to permit of universal movement to a moderate degree, and also 

 fitted with draw-bar springs to allow of variations in length due 

 to surging and pitching. The ball-and-socket principle was embodied, 

 not in the pipe itself, but in a strong steel frame above the pipe, which 

 was connected by rubber sleeves in the usual manner. This has 

 proved entirely successful, and the practical result is that the dredge 

 is capable of continuing at work in all but the heaviest weather. 



