A HISTORY OF SCIENCE 



earth's meridian made by the French astronomer 

 Picard. The new measurement made a degree of the 

 earth's surface 69.10 miles, instead of sixty miles. 



Learning of this materially altered calculation as to 

 the earth's size, Newton was led to take up again his 

 problem of the falling moon. As he proceeded with 

 his computation, it became more and more certain that 

 this time the result w r as to harmonize with the ob- 

 served facts. As the story goes, he was so completely 

 overwhelmed with emotion that he was forced to ask 

 a friend to complete the simple calculation. That 

 story may well be true, for, simple though the com- 

 putation was, its result was perhaps the most wonder- 

 ful demonstration hitherto achieved in the entire 

 field of science. Now at last it was known that the 

 force of gravitation operates at the distance of the 

 moon, and holds that body in its elliptical orbit, and 

 it required but a slight effort of the imagination to 

 assume that the force which operates through such a 

 reach of space extends its influence yet more widely. 

 That such is really the case was demonstrated presently 

 through calculations as to the moons of Jupiter and by 

 similar computations regarding the orbital motions of 

 the various planets. All results harmonizing, Newton 

 was justified in reaching the conclusion that gravitation 

 is a universal property of matter. It remained, as we 

 shall see, for nineteenth-century scientists to prove 

 that the same force actually operates upon the stars, 

 though it should be added that this demonstration 

 merely fortified a belief that had already found full 

 acceptance. 



Having thus epitomized Newton's discovery, we 



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