84 IRRIGATION FARMING. 



steel shall lie around the pipe. These short cylinders 

 are then double-riveted along the straight seam, using a 

 good quality of Swedish or Norway iron. By means of 

 traveling cranes and numerous supports seven or eight 

 of the short lengths are afterwards continuously riveted, 

 making a section of completed pipe of from twenty to 

 twenty-five feet long. A section of this pipe may be seen 

 in Figure 21. 



Only one row of rivets is inserted in the end or 

 round seams, and the joint is made by expanding one 

 end by means of specially devised machinery, by accom- 

 plishing the same object in riveting, or by making an 



FIG. 22. SPIRAL IKON PIPE. 



equal number of large and small cylinders so that the 

 end of the smaller can be driven into the end of the 

 larger and riveted. 



Spiral iron pipe, shown in Figure 22, is made in much 

 the same way, and some advantages are claimed for it by 

 manufacturers. 



Laminated Iron Pipe. In California twenty years 

 ago the irrigators used plain sheet-iron pipes, which soon 

 corroded so badly that they were worn-out completely 

 and had to be taken up. The life of a sheet-iron pipe 

 depends on its coating, and without some protection 

 against oxidation the shell of the pipe will soon be con- 

 sumed by rust. Wrought iron laminated asphalted pipe- 

 arc made of two shells of sheet iron. These shells are 

 made of one sheet of iron eight feet long, rolled and hip- 

 ped one inch, and united by a composition solder. They 

 are half the thickness of iron that would be necessary 



