THE NATIONAL RESEARCH COUNCIL 25 



in Chapter 14. Another means of improving the quality of 

 steel has been supplied by the development of a pyrometer 

 suitable for measuring the temperature of steel baths in fur- 

 naces. One of the most important of the metallurgical prob- 

 lems attacked was that of the fatigue phenomena of metals. 

 The results of this investigation show that the elevation of the 

 elastic limit of steel, caused by such processes as cold rolling 

 and wire drawing, is dissipated by the repetition of a wide 

 variation of stresses, as in aircraft crank-shafts, which may 

 ultimately break down from this cause. 



The development of certain war inventions was another im- 

 portant function of the Engineering Division. A staff of de- 

 signers and draftsmen, starting in some cases with well-defined 

 schemes and in others with very nebulous suggestions, worked 

 out the designs of promising devices, some of which proved 

 very effective in military practice. An interesting activity of 

 this branch of the Division, carried out in conjunction with 

 the Science and Research Division of the Signal Corps, re- 

 sulted in the production of small balloons, capable of maintain- 

 ing themselves automatically at any desired altitude, by al- 

 ternately throwing out liquid ballast and releasing gas. Bal- 

 loons only nine inches in diameter (before inflating) adjusted 

 to float at the altitude of a known prevailing air current, 

 traveled easterly from Fort Omaha for a distance of nearly 

 1000 miles. It is now proposed to use such balloons to ascer- 

 tain the air currents above the Atlantic between the American 

 and European coasts. 



In the field of Geology and Geography the opportunities 

 for war activities were more numerous than one might sup- 

 pose. (See Chapters n and 12.) The importance of utiliz- 

 ing geologists for service at the front was fully appreciated by 

 the enemy, and a memorandum describing German methods, 

 and indicating the usefulness of geological advice in military 

 operations was presented to the Secretary of War in 1917 by 

 the Division of Geology and Geography of the Research Coun- 

 cil. A considerable development of such service took place in 



