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ROYAL SOCIETY 01- CANADA 



the strength proportioned to the head of water, ri vetted with a double 

 row on the straight seams and single on the round. According to ^Fr. 

 llobson. General Manager, Cariboo Hydraulic Company, ir» n is 

 preferable to steel, because the latter is often of uneven temper, having 

 hard spots which break in bending ; besides which steel is more readily 

 attacked and eroded with rust than even the common quality of sheet 

 iron. The best quality of sheet iron has had, in hydraulic pipes, four 

 times the length of life of the best quality of steel. 



The sections are made up in lengths of fifteen to eighteen feet, 

 such as can be conveniently handled by two to four men as the pipes 

 may vary from fifteen to thirty inches in diameter ; and are put to- 

 gether on the ground " stove-pipe fashion," caulked by sacking and 

 driven home by a Avooden ram, eight inches diameter by six feet long." 



Though not frequently exposed to the pressure due to the hydro- 

 static head, these pipes are strong enough to resist this when necessary. 

 Mr. Hobson states that " such iron pipe has been in use for years under 

 a tensile strain of 13,000 pounds to the square inch, although," he adds, 

 '' most authorities would hardly admit this factor of safety." He gives 

 the safe pressure for the three sizes of pipes used by his company as 

 follows : 



These pipes, which are bell-mouthed, should be as large in dia- 

 meter as can be afforded, to lessen the friction and increase the force 

 of the issuing stream, and because their size must be decreased in 

 approaching the giant so that here they can be easily handled by man 

 power, in the frequent changes of position necessary. 



Sheet iron pipes treated by immersion in a hot bath of asphalt have 

 been in use in California, some for more tlian a quarter of a century, 

 and are subjected to great pressures as shown in the following table, 

 published by the Joshua Hendy Machine Company, San Francisco : — 



