HALIFAX WATER WORKS. JOHNSTON. 105 



case of, the 27-inch, a leak developed during the winter follow- 

 ing the laying of the pipe, and on digging down to the main a 

 joint w 7 as discovered to have drawn out about J of an inch. 

 This was caulked with cold lead and gave no trouble until the 

 following winter, when it again showed signs of leaking, and on 

 investigation the joint was found to have drawn another ^ inch. 

 The blocking of the pipes on each side had apparently not 

 settled out of place, being laid on the top of the ledge rock. It 

 was thought that this drawing apart of the joint might have 

 been due to the contraction of the pipes. Assuming the differ- 

 ence of temperature to have been 30 degress, which is a fair 

 estimate between the temperature of the pipes when laid and 

 when the leak developed, the contraction to open the joint f 

 inch would have to take place through 324 feet of pipe. If this 

 took place on each side of the defective joint there would be a 

 strain on the joint of over 16 tons, the pipes weighing a ton 

 and a quarter to the 12-foot length, if the leakage was from this 

 cause, it should close up again in the summer when the tem- 

 perature of the pipe rose. Unfortunately, the | inch which is 

 said the pipes separated in the second winter was not measured 

 accurately, but was estimated by the foreman and may have 

 been overstated ; but assuming it to be correct, the writer can- 

 not advance any theory for the increase in the opening from 

 this cause, as there would not be any more difference in the 

 temperature than the amount given above. It is possible that 

 the joint may not have been driven home, and as at this point 

 there was only about four pounds pressure when testing, the 

 oxide paint used may have prevented the leak showing when 

 the pipe was tested on being laid, and a settlement may have 

 occurred in one or two lengths of pipe distant from the leak 

 dragging the pipe apart at the weakest point. 



It will be seen from the description of the method of laying, 

 that the process of lowering and blocking is exactly the same as 

 for plain pipe, except the ramming home, which takes but very 

 little more time than the extra care required in centering the 

 pipe for a lead joint and then the joi-nt is complete; whereas, 



