160 



STREET-MAINS. 



Fig. 38. 



I 



of mains from nine to fifteen and eighteen inches diameter. The usual thick- 

 ness of metal is shown by the hatched lines, and is proved to be sufficient ; 

 the pipes are occasionally made the thickness marked by the outside line ; 

 the reason given being that " thinner metal cracks in making the joints." This 

 is an erroneous idea, since the extra strength must depend on the width of the 

 bead from a to b. The depth of these sockets is 4^ inches. 



No. 2. is a section of the sockets of mains from four to eight inches diame- 

 ter ; their depth four inches. 



No. 3. is the thickness of those of a smaller diameter, three inches deep. 



The thickness of the main pipes ought to be as follows : 



inches diameter 



inch thick. 



4 

 5 

 6 



8 



full. 



f -full. 



2 



5 

 6 

 5 



'S 



3_ 



4- 



3 



f 



I 



inch thick. 

 full. 



The throat of the socket a little stronger, as shown in Fig. 38. 



The annular space left between the bead end of one, and socket of the next 

 pipe, should be about half an inch in the large mains, and not less than three- 

 eighths in the small. The diameters of the sockets must therefore be guided 

 by this. 



