THE WORLDS ADVANCE 



303 



tion was about five feet in length. The 

 sections of cement were buried two feet 

 in the ground, thus leaving three feet of 

 the wall exposed to view. 



The unique wall stands up alone, there 



being nothing to reenf orce it. The points 

 where the sections meet are not even ce- 

 mented together. Without having cost 

 the owner a cent, this feature serves the 

 purpose of an expensive retaining wall. 



AN AUTOMOBILE THAT TRIED TO 

 TRAVEL UNDERGROUND 



The latest method of travel to be in- 

 augurated is that of automobiling under- 

 ground at least a large touring car re- 



$40,000 : THE PRICE OP A STRAIGHT 

 LINE 



It is very difficult to make a perfect 

 straight edge. We think a ruler has a 

 straight edge, or that the edge of a knife 

 or table or stone is absolutely 

 straight, but they are far from 

 it. 



One of the most difficult 

 problems in practical mechan- 

 ics is to make a straight edge. 

 How difficult it is may be 

 judged from an incident that 

 occurred in the shop of a cele- 

 brated astronomical instru- 

 ment maker. 



Two Views of a Strange Accident tha 

 Befell a Powerful Touring Car. Although 

 the Automobile Made a Large Hole in 

 the Ground, the Only Damage it Sustained 

 was in the Form of a Bent Front Axle 

 and Damaged Front Mud Guards. 



cently tried to establish an underground 

 travel era, and not through a hole in the 

 ground either. 



The automobile in question attempted 

 to dig its way underground, occupants 

 and all, but through lack of strength it 

 failed, as the illustration shows. No one 

 was injured by the accident, and after 

 the automobile was pulled out of the hole 

 it was learned that no more damage had 

 been incurred than the bending of the 

 front mud guards and front axle. 



A patron asked what would be the 

 price of "a perfect straight edge of glass 

 thirty-six inches long." 



"It cannot be made perfect," said the 

 instrument maker, "but it" could prob- 

 ably be made with a limit of error 

 amounting to only a fraction of a wave 

 length of light." 



"How much would that cost?" 



"About $40,000." 



It turned out that the customer wanted 

 the straight edge for a scraper and that 



