284 TOWERS AND TANKS FOR WATER-WORKS. 



driven, while the other two strike in turn upon the hammer 

 held by the riveter in forming the field-head. Two extra 

 laborers are generally employed to work at the winch and to 

 sort out material as directed by the foreman. 



Such a crew will drive from 400 to 500 rivets per day of 

 ten hours, at a cost of 3 cents each, or the entire cost of 

 erection, including riveting, will amount to about $20.00 per 

 ton of material. The scaffolding is left in place upon the in- 

 side of the tank until after testing by filling. The tank being 

 tight, it is then removed. Instead of the scaffold as de- 

 scribed, a floating scaffold is sometimes employed, which 

 consists of a buoyant platform or float that is raised to 

 position as required by pumping water into the tank. 



Inspection. After inspection and approval of the metal- 

 work and the emptying of the water used in testing, the in- 

 terior surfaces should be wiped dry with oily cloths, and the 

 final coating or painting given, the scaffolding being re- 

 moved as the painting proceeds from the top downward. In 

 view of the fact that a heavy gale is liable to seriously affect 

 the joints of the stand-pipe if empty, by straining the struc- 

 ture, immediately upon the drying of the paint, the reservoir 

 should be filled with water and kept so filled until put into 

 actual use as part of the water system. 



Erection of Towers and Tanks. In the erection of a 

 tower, the pedestal-plates should be bedded in cement mor- 

 tar about an inch thick. The first step toward erection is to 

 conveniently place the columns and members of the first panel 

 or section, and in such position that, with the aid of a stout 

 gin-pole, blocks, tackle, and winch, the columns may be 

 simultaneously raised to their vertical position and the hori- 

 zontal members placed and temporarily fastened with bolts, 

 to be subsequently riveted before proceeding with the next 

 panel or deck. 



As has been remarked, the field-riveting should be con- 



