I9I0.] DAVIES— TUNNEL CONSTRUCTION. 187 



immense bridges which, on account of the lateral strength and 

 rigidity, must be built on an enormous scale, whereas tunnels can 

 be constructed on any lines, wherever they will give the greatest 

 facilities for distribution of the travelling public. 



New York City, and in fact all of our great cities, are absolutely 

 in their infancy in respect to the tunnel for transportation. There 

 is practically no limit to the development of this line of work 

 as the necessities arise and as traffic demands, and we have reached 

 in New York City a point where the possible construction of tunnels 

 can hardly, by any possibility, keep pace with the growth and de- 

 velopment of the population and with the necessities for their trans- 

 portation. 



In respect to the rivers, the future, unquestionably, has wuthin 

 sight construction of highway tunnels between New York and New 

 Jersey on the lines of the Blackwall under the Thames in London 

 or similar tunnels under the Clyde at Glasgow, forming under- 

 ground extensions of existing street thoroughfares; and the object 

 of this presentation of the subject is to give an accurate idea of 

 the principles underlying the construction of such arteries of trans- 

 portation. 



