I igure 36. — Interior of Beach Sub- 

 way showing iron lining on curved 

 sei tion and the pneumatically pow- 

 ered passenger car. View from 

 waiting room. {Scientific American, 

 March -,, 1870.) 



Enlarged versions of the Beach shield were used in a 

 few tunnels in the Midwest in the early 1870's, but 

 from then until 1886 the shield method, for no clear 

 reason, again entered a period of disuse finding no 

 application on either side of the Atlantic despite its 

 virtually unqualified proof at the hands of Greathead 

 and Beach. Little precise information remains on 

 this work. The Beach system of pneumatic transit is 

 described fully in a well-illustrated booklet published 

 by him in January 1868, in which the American In- 

 stitute model is shown, and many projected systems 

 of pneumatic propulsion as well as of subtenant. m 

 and subaqueous tunneling described. Beach .mam 

 (presumably) is author of the sole contemporary at - 

 count of the Broadway Subway, which appeared in 

 Scientific American following its opening early in 1870. 

 Included are good views of the tunnel and ear. ol the 

 shield in operation, and. most important, a vertical 

 sectional view through the shield (fig 



It is interesting to note that optical surveys for 

 maintenance of the course apparently were not used. 



The article illustrated and described the driving each 

 night of a jointed iron rod up through the tunnel 

 roof to the street, twenty or so feet above, for "testing 



the position.'" 



THE FIRST HUDSON" RIYLR TUNNEL 



Despite the ultimate success of Brunei's Thames 

 Tunnel in 1843, the shield in that case afforded only 

 moderately reliable protection because of the fluidity 

 of the soil driven through, and its tendency to enter 

 the works through the smallest opening in the shield's 

 defense. \n English doctoi who had made physio- 

 logical studies ol the effects on workmen of the high 

 air pressure within diving bells is said to have recom- 

 mended to Brunei in 1828 that he introduce an 

 atmosphere of compressed air into the tunnel to ex- 

 clude the water and support the work face. 



I Ins plan was nisi formally described b) Sir Thomas 

 ( i« In. me (1775 I860) in a British patent of 1830. 

 Conscious of Brunei's problems, he proposed a system 

 of shaft sinking, mining, and tunneling in water- 

 bearing materials by filling the excavated area with 



PAPER 41: TUNNEL ENGINEERING — A MUSEUM TREATMENT 



231 



