THE STORY OF A GREAT WORK. 467 



and a half, the space under the tube when the shield moved for- 

 ward was filled with cement. The clay was allowed to settle 

 down on the upper part. When the shields met, the tube was 

 built up within them to the junction and the shells of the shields 

 allowed to remain. The inside of the tube is finished with a 

 preparation to keep it from rusting. 



On Sunday, August 24, 1890, the two excavations had ap- 

 proached so nearly that an opening was made with an earth 

 auger, and the workmen talked and passed articles to each other. 

 The earth was soon removed, and Mr. Hobson, the chief engi- 

 neer, and others connected with the tunnel company, stepped 

 through. Six days later the shields came together and the suc- 

 cess of the great undertaking was assured. In its construction 

 about seven hundred men were employed, of more than average 

 intelligence, who took great interest in the work. 



The actual length of the tunnel, from portal to portal, is six 

 thousand and twenty-six feet. Of this, two thousand three hun- 

 dred and ten feet is under the river, one thousand nine hundred 

 and eighty-two feet under dry ground on the Canada side, and 

 seventeen hundred and thirty-four feet under dry ground on the 

 United States side. The open excavation to reach the ground 

 level on the Canadian side is three thousand and sixty-one feet, 

 and on the United States side two thousand four hundred and 

 sixty-six feet. The grade is one in fifty, except under the river, 

 where it is practically level, only sufficient incline one tenth per 

 cent being given toward the Canadian side to provide for drain- 

 age. The depth of the lowest part under the mean level of the 

 river is 77'83 feet. The minimum depth between the top of the 

 tube and the bottom of the river is fifteen feet, the average being 

 twenty-five feet. It was necessary to place it as far down as pos- 

 sible in the clay, consistent with the grade, so as to overcome the 

 tendency of a tube filled with air to rise to the surface in water 

 or mud. The bottom is about nine feet above the rock which 

 underlies the clay. On the Canada side the bottom is sixty feet 

 below the surface of the ground at the portal, on the United 

 States side it is eight feet less. The bottom of the tunnel at its 

 lowest point is one hundred feet below the railway track on the 

 level, which indicates the total ascent and descent which trains 

 have to make in passing through. Ventilation is secured by the 

 motion of the trains, which is found to be ample for the purpose. 



The trains are drawn through the tunnel by powerful locomo- 

 tives belonging to the tunnel company, specially built for the 

 purpose. They take eighteen loaded cars at a trip. 



The track in the tube is supported on solid brickwork, as 

 shown in the accompanying cross-section. It was at first proposed 

 to build the tunnel wide enough for two tracks, but it was found 



