THE HOLLAND TUNNEL GRAY AND HAQEN 597 



at a time, the width of a section, by means of 30 liydraulic jacks supported 

 against the end of the tunnel alrojidy liuilt. Several of the jacks were then 

 removed and a segment was hoisted into place by a tremendous erector arm 

 till a complete ring had been added, and then the shield was forced ahead 

 again. Doors in the lower part of the shield allowed about 30 per cent of 

 the displaced compressed silt to enter the tunnel on each shove. 



We stood watching the big burly men as they shoveled the df-bri.s into the 

 cars that carried It out through the lower air chambers. Not particularly 

 envious of them at such hard labor, we listened only half-heartedly to our 

 guide until he remarked that the automobiles we had seen parked at the 

 entrance belonged to these very " .=and-hogs '* ; that they miide high wages 

 and worked short hours. There are laws forbidding their working In com- 

 pressed air for more than two hours at a time for health reasons. Law like- 

 wise requires the company emi)loying the men t<) furnish hot showers and hot 

 coffee for them when they come out. 



From the digging wo turned to watch the erector ; two men tugging at a 

 mammoth wrench tightening the bolts : the grouting machine as It forced its 

 mixture with pressure beyond the segments to form a concrete shell for the 

 whole tube; and then to discuss the miracle that prevented the Hudson itself 

 from pouring in on us in one deluge. There we stood with only a few feet of 

 sand and gravel between us and the river. 



"Chief" Holland and the rest of the engineers chatted with us as casually 

 as if it were a game of tiddle-de-winks they were explaining, instead of an 

 aclilevement that even seeing denied believing. We picked up bits of rock for 

 souvenirs and continued gasping when one of our hosts turned questioner. He 

 asked if we could whistle. 



Assuring him that whistling did not stump the modern girl, we inquired his 

 preference as to a tune. He consulted the other men. and after much deliber- 

 ation proposed to give us a big party on the condition that we whistle "Yankee 

 Doodle" — all five verses. W^ith one accord lips were puckered and cheeks 

 distended. Our chagrin was only equaled by the laughter of our tormentors 

 as we puffed and blew in vain. The party was given for effort and not for the 

 results obtained against 20 pounds of pressure. 



In quitting the compressed air it was necessary to put on fleece-lined coats 

 to prevent catching cold. We retraced our steps through the man lock, where 

 the pressure was reduced gradually back through the tube, and insisted on the 

 law requirement of hot coffee on signing off. 



The problem of ventilation of the Holland Tunnel was unlike any 

 heretofore solved, both in character and magnitude. The only exist- 

 ing vehicular tunnels even approximately comparable to the Holland 

 Tunnel are the Blackball and Rotherhithe Tunnels under the Thames 

 at London. 



The Blackwall, opened for traffic in 1897, has an under-river length 

 of 1,221 feet between shafts. It consists of a single tube 27 feet in 

 diameter with a roadway accommodating one line of traffic in each 

 direction and two sidewalks. Traffic counts in 1920 showed that the 

 maximum number of motor vehicles using the tunnel was less than 

 100 per hour. 



The Rotherhithe is 30 feet in diameter, similar to the Blackwall 

 in traffic facilities, with an under-river length between shafts of 1,570 

 28095—31 39 



