SCIENTIFIC OFFENSIVE 



variations cause a small beam of light to move across a 

 slowly-traveling strip of photographic film, to be de- 

 veloped and analyzed later; (5) telemeter-recording 

 systems, in which pressure values are actually broad- 

 cast by small, automatic, radio transmitters to wait- 

 ing recorders located in some convenient places several 

 miles away; (6) permanent-deformation gages, such 

 as the Penney cans, which undergo permanent de- 

 formations easy to interpret. 



A second requirement was that the gages be really 

 rugged. Despite the need for using ingenious record- 

 ing systems, the gages and their mounts must survive 

 the terrific overpressure. It is pointless to use a pre- 

 cision gage which is promptly flattened or blown over- 

 board.* Hence delicacy was not a characteristic of 

 the instrument cases taken to Bikini ; on the contrary, 

 many of the designers enclosed their instruments' deli- 

 cate worki^ in cases built of 2-inch-thick steel which 

 could withstand the pressure. 



In the third place, the gages must resist corrosion. 

 In the hot humid air, metal objects corroded unusually 

 rapidly. Aluminum apparatus was, of course, very 

 vulnerable to salt water. Thus corrosion-resistant 

 metals were used ordinarily for exposed working parts, 

 or waterproof coatings of paint or lacquer were ap- 

 plied. 



* In the Alamogordo test of June 16, 1945, a number of instru- 

 meyxts failed to stand up to the U7iprece dented pressures. Some 

 were crushed, others were torn loose and thrown considerable dis- 

 tances. 



65 



