Popular Science Monthly 



329 



iff ft 



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through treacherous and rotten rock, and has to be built without disturbing the traffic in the 

 present interborough subway, which is to be seen on the second level in the illustration 



perilotis. New underground routes are 

 being driven through some of the world's 

 most crowded streets, and without mate- 

 rially interfering with the traflic. Though 

 the typical construction is a covered 

 ditch with a roof which is only a foot or 

 two below the floor of the street, there 

 are many places where real tunneling 

 and mining operations are rec|uired. The 

 digging goes on under a variety of con- 

 ditions : through imderground swamps 

 and watercourses, through treacherous 



rock, through sand and even through 

 quicksand. At the south end of Man- 

 hattan Island two new sets of tubes are 

 being driven under East River; at the 

 north end a set of tubes was built on 

 shore and then towed out into place and 

 sunk on the bed of the river. In Lex- 

 ington Avenue a new idea in subway 

 l)uilding is i)resented in the form of an 

 underground double-decker. At Grand 

 Central Station the earth is being honey- 

 combed into five k'\els. 



