. .1.1 : MAX MKTHOI) 1 .">.") 



filling. Earth packing was tried, but gave still worse results. 

 Finally dry rubble tilling was adopted, with satisfactory results. 

 There was necessarily some sinking of the surface. This re- 

 sulted partly from the necessity of changing and removing of 

 tlu- timlwrs, and from the compression and springing of the 

 timbers under the great pressures. The crown of the arch also 

 settled from 2 ins. to 6 ins., due to the compression of the 

 mortar in the joints. The maximum sinking of the surface of 

 the street over the tunnel was about 18 ins.; it usually ran 

 from 1 to 1 2 ins. Some damage was done to the water and gas 

 mains. This damage was not usually serious, but it of course 

 necessitated immediate repairs, and in some instances it was 

 found best to reconstruct the mains for some distance. At one 

 point along the tunnel where very treacherous material was 

 found, the surface settlement caused the collapse of an adjacent 

 building, and necessitated its reconstruction. 



