Photo from Bureau of Standards 



A RAII. THAT FAILliD 



This cross-section of a rail which failed under the pressure of a passing train_ shows 

 numerous flaws in the steel. At present there is no certain means of ascertaining if such 

 flaws exist without cutting into the rail, and thereby rendering it useless. The Bureau of 

 Standards is working to discover tests which will be both accurate and applicable to the 

 rails actually to be used on the permanent way. 



behavior of aneroid barometers, which 

 are of the greatest interest to the geog- 

 rapher, to the explorer, the surveyor, the 

 mountaineer, and the aviator, for the 

 aneroid is an instrument of the highest 

 importance in their work. 



WHY aviators' r'iGURElS ARF, UNRELIABLE; 



Experiments show that the effect of 

 temperature is usually negligible com- 

 pared with the mechanical and elastic 

 errors to which even instruments by the 

 very best makers are liable. It has been 

 found that an aneroid carried slowly up 

 the side of a mountain will give an en- 

 tirely dift'erent reading to that given when 

 taken rapidly up the same mountain in 

 an electric railway. 



As an instrument for measuring height 

 it has been proved very unreliable unless 



thoroughly studied ; sc that when an 

 aviator announces from the readings of 

 his instrument that he has made an as- 

 cent of 15,748 feet his figures may be 

 promptly discounted, the real truth be- 

 ing that the ascent was probably about 

 15,000 feet or even less, or that it might 

 have been over 16,000 feet, depending 

 upon the method of making the instru- 

 ment. 



To show how unreliable such figures 

 are when uncorrected, seven aneroids of 

 the best-known make, each of them as 

 fine an instrument as could be procured 

 on the market, were taken up together 

 in the same aeroplane. The ascent was 

 made, the height recorded, and the ma- 

 chine descended. Then the readings of 

 the seven aneroids were examined, and 

 it was impossible to find out how high 



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