d ambiguous" A A a Brillouin, op. cit., p. 52. ficeThe model need . .. we observe it" A A 25. Max Born, Experiment and Theory in Physics (New York: Dover Publications, Inc., 1956), p. 39. ficeA physical quantity . . and measure it.fi A A 26. Jeans, op. cit., p. 172. ficeThe making of . . . away from reality" A A 27. S