DISCOVERY OF THE NEUTRINO — COWAN 



411 



amount of energy each measure of powder has in it, he calculates again 

 how far the charge should carry each bullet. 



Back on the rifle range, the bulletmaker again fires his new bullets, 

 and again, none goes far enough. He checks his gun again and again, 

 then fires good, old-fashioned bullets using powder that has worked 

 well for years. These behave perfectly. Each falls at exactly the 

 right place. But when he tries his new powder, none of the bullets 

 behave sensibly. He checks for gas leakage from the rifle breech. 

 There is none. Pie examines the shells after firing. The powder has 

 burned perfectly and completely. Tormented by the puzzle, the master 



' — ' ' ^ 



bulletmaker drives himself to discover where the loss of power is occur- 

 ring. After firing bullets for some weeks, the spent bullets lie in a long 

 continuous heap stretching down range from his gim. 



By now, many of the bulletmaker's friends have heard of his strange 

 problem and visit his rifle range to see for themselves. Of course, 

 each has an opinion, and each is invited to correct the difficulty. They 

 fire the bullets with their guns, but the bullets merely fall onto the 

 growing pile. They test the powder over again, but find that it always 

 burns completely and at the same rate. Many end by shaking their 

 heads and declaring that the bulletmaking craft is no longer an exact 

 science, that the familiar rules can no longer be relied upon. 



One friend, however, takes a meter stick and measures the dimen- 

 sions of the pile of spent bullets. He measures its depth at various 

 distances from the gun. Then he makes a suggestion (for he doesn't 

 want to give up the rules so readily). "Suppose two bullets come 

 out of the gun at each firing with this new powder ! One would be 

 the bullet seen to fall onto the pile, and the other a very small one 

 which travels a great distance at high speed and is not seen. The new 



