644 



Popular Science Monthly 



had just removed some of the shoring 

 when earth began to drop rapidly away 

 from one spot in the top of the tunnel. 

 One of the men seized a bag of cement 

 which is kept for such an emergency and 

 attempted to block up the rapidly 

 growing hole. Suddenly there was a 

 report like a pistol shot. His startled 

 comrades saw the man jerked up out 

 of sight. Then they realized what hap- 

 pened. The man 

 had been blown 

 away like a pea in 

 a pea-shooter. One 

 of the men managed 

 to save himself by 

 clinging to the 

 shield. The other 

 two victims were 

 shot upwards to 

 the surface of the 

 river. 



The instant that 

 the work of rescue 

 had been complet- 

 ed, officials began 

 the work of repair. 

 It was found that 

 the accident had 

 been caused by a 

 spot in the bed of 

 the river which had 

 been unable to 

 withstand the air 

 pressure of twenty- 

 four pounds to the square inch that 

 had been maintained in the tunnel. 

 As a result the bottom of the river had 

 blown out like a faulty automobile tire 

 when overcharged with air. 



Only once before in the history of 

 tunneling has a workman been shot 

 through the bed of a ri\'er and survived. 

 Eleven years ago a "sand hog" was 

 blown through the bed of the East River 

 during the construction, of the present 

 subway system. Although severely in- 

 jured he survived the shock, and by a 

 curious coincidence was working on the 

 tunnel in which the recent accident 

 occurred. 



Militia Aero Corps 



TWENTY-FOUR states are at pres- 

 ent organizing aero corps to be in- 

 cluded in their National Guards and 

 Naval Militias. 



Spikes help a lineman to climb a wooden pole, 

 but not a pole of steel. A shoe has been in- 

 vented which enables a lineman to clamp him- 

 self step by step on the steel pole 



Climbing Steel Poles with the Aid of 

 Iron Shoes 



IT was always an easy matter for a line- 

 man to stick the points of his climbers 

 into the sides of a wooden pole and 

 reach the top with the agility of a 

 squirrel. With the introduction of steel 

 poles for high tension electrical lines, 

 some other climbing help had to be 

 found. A forged steel shoe has been 

 invented, which is 

 neatly strapped 

 over the regular 

 shoe. 



The toe of the 

 steel pole - climber 

 curves upward. On 

 its tip there are two 

 steel projecting 

 bearings or clamp- 

 ing points, and 

 these points tell the 

 secret of the device. 

 A square steel 

 block, having four 

 sharp corners is 

 placed just beyond 

 the toes of the 

 steel shoe. When 

 dull from use these 

 corners may be 

 substituted one for 

 another. 



This special block 

 bears on the out- 

 side of the steel pole, and a steel point 

 situated at the end of the climber bears 

 on the opposite side. 



The climbers have a clamping action 

 between the block and the point on the 

 edge of the steel pole. This action is 

 accomplished by the pressure of the 

 lineman's weight on the end of the 

 climber. Naturally his weight will come 

 at the right point in climbing the pole. 

 As he raises his foot for the next step, 

 the lifted heel releases the grip of the 

 climber. The steel climbers weigh about 

 as much as the old style grippers used 

 for the wooden poles. 



An Invisible Ink 

 'HEN the juice of an onion or 

 lemon is substituted for ink, no 

 visible effect is made on the paper until 

 heated, when the writing will stand out 

 very plainly. 



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