596 ANNUAL. REPORT SMITHSONIAN" INSTITUTION, 19 3 



Chief Engineer Holland himself greeted us, and began an introduction to 

 this vast engineering project with maps, diagrams, and more maps and dia- 

 grams, till red lines showing tunnels, and blue lines showing traffic lanes, and 

 green lines showing river bed swam before our gaze. We nodded very know- 

 ingly, mumbled pleasantly that exquisite shades had been chosen for the 

 various lines, and moved on to the doctor's office. 



Here we were introduced to the necessary procedure before going into 

 compressed-air chambers. Ears, heart, and blood pressure were examined. 

 As we were found physically fit, we were passed on to the wardrobe, where 

 we were presented with an assortment of khalci cover-alls and left to our own 

 discretion as to choice. 



The first twinge of squeamishuess about cleanliness was quickly dispelled 

 by the romatic second thought that the very men who were performing this mir- 

 acle under the river had worn these self-same garments. Then followed a 

 scramble for the most bespattered on the theory that such muck was a mark 

 of courage in dashing into subaqueous passages. Size was completely disre- 

 garded. Never in all the stages of dressing up to set forth for adventure in 

 my childhood days had I enjoyed more of a thrill as so arrayed we followed 

 our guides to the tunnel entrance. 



Once inside we were amazed to find what a simple form such a complex 

 sounding work could assume. The tubes are made of cast-iron segments bolted 

 together. Fourteen of these sections are required to make a complete ring. 

 PJach section weighs 1^2 tons and is held in place by huge bolts weighing 10 

 pounds. 



" Oh's " and "Ah's " were vented as we continued our way to see the actual 

 excavating. We passed groups of men sitting about talking, laughing, and 

 playing cards, awaiting their shifts. Work was never stopped 24 hours a day, 

 7 days a week. (With an investment of $42,000,(KX), it was imi)erative that no 

 time be lost.) We met car after car of excavated material on its way down the 

 temporary tracks to the entrance and out to be dumped. 



At last we arrived at the great concrete bulkhead that sealed the compressed- 

 air section, separating it from the completed portion of the tunnel. 



The bulkhead contained four air chambers or locks. Two large compartments 

 at the bottom of the bulkhead were equipped with tracks for bringing supplies 

 to the workers and for removing the excavated material. Two smaller cham- 

 bers were provided in the upper section for the workmen who on entering and 

 leaving the tunnel must be gradually brought from one pressure to another. 



We entered one of these (only one was used normally, the other reserved 

 for emergencies) and saw the iron door clanged to and fastened. Then followed 

 lessons in equalizing the pressure inside and outside the head by holding the 

 nose and " snorting " — very much as one does when trying to expel water from 

 the nose after diving. The danger of the " caving in " of one's eardrums 

 was stressed, and we were warned to hold up our hand the moment the pressure 

 became too severe. This was the only way to attract the attention of the man 

 who turned on the compressed air, as the noise made even shouting inaudible. 



We sat wild-eyed, expecting the hideous monster to leap upon us any minute. 

 The bark was worse than the bite. Twice we raised our hand and the pressure 

 was turned ofE until the pressure in our ears was relieved. When the 29-pound 

 mark was reached the door leading into tlie high-pressure section was opened, 

 and there we were in the very midst of the digging. 



Once accustomed to the pressure, it was not noticeable, and we began a 

 siege of questions about the actual excavating. 



This work was done under a shield, or movable head, slightly larger than 

 the external diameter of the tunnel. The <iliicld was forced forward 2% feet 



