TINMIUM; MKTMODS 



195 



found disintegrated and alternated with strati of loose soils, 

 and even pockets of quicksand will be met with along the line 

 of the road. 



Cross-Sections. The section of the underground road will 

 be of three different types, the rectangular, the barrel-vault, 

 and the circular. The rectangular section, Fig. 113, will be 

 used for the greater part of the road, of which a portion will 

 be for four tracks and a portion for two tracks. The dimensions 

 adopted for the four tracks are 50 x 13 ft., and for the double 

 tracks 25 x 13 ft The barrel- vault section, composed of a 



"" "KSSSSlA 



Fio. 113. Double Track Section, New York Rapid Transit Railway. 



poly centric arch, having the flattest curve at the crown, has been 

 adopted for the tunnels under Park Avenue wink- the semi- 

 circular arch is used for all the other portions of the road to be 

 tunneled. The circular section of 15-ft. diameter will be used 

 under the Ilarlrm River, and being for single track, two parallel 

 tunnels will In- built side by side. 



The main line from the post-office loop to about 102d 

 St., consists of four tracks built side by side in one conduit, 

 except for that portion under the present Fourth Ave. 

 tunnel when- t\v<> parallel double-track tunnels will l>e em- 

 ployed. The West Side Line will consist of double tracks 



