86 BULLETIN OF THE 



posed that the author copied it from some old authority ; that he 

 was not guilty of inventing it, abused as it was. 



Iu " Hind's Dictionary of Arts and Sciences" (one volume, folio, 

 London, 1769, copy in the Congressional Library) it is found under 

 the article " Attraction." 



The first named author announced that " Gravity at different dis- 

 tances from the east must vary inversely as the square of the dis- 

 tances." He proceeded substantially as follows : 



" The total amount of attraction exerted by the earth upon bodies 

 exterior to it is the same as though that force was all concentrated 

 in the centre. But a force or influence which proceeds, in right 

 lines from a point in every direction is diminished as the square of 

 the distance is increased. For, let the centre of the earth be the 

 vertex of a pyramid, cut said pyramid by two parallel bases at 

 different distances from the vertex, making two similar pyramids. 

 Whatever the nature of gravity, its influence at the distance of each 

 base must he equally diffused over the base. Therefore its intensity or 

 force will be as much less at the greater base, as contrasted with its in- 

 fluence at the nearer and lesser base, as the surface of the latter is to 

 the surface of the former. But the surfaces of these bases are to 

 each other as the squares of their distances from the vertex. There- 

 fore the force of gravity varies inversely as the square of the dis- 

 tances.— Q. E. D." 



Actually he placed Q. E. D. to it as if it was a mathematica, 

 demonstration ! 



He afterwards said : 



" The intensity of light at different distances from the radiant 

 varies inversely as the square of the distances. This proposition is 

 proved in the same manner as that respecting gravity, the reasoning 

 in, which applies to all emanations from a centre." 



Subsequently, when he got to refer to the laws of Kepler, he 

 said: 



" They, therefore, became known as facts before they were demon- 

 strated mathematically. The glory of this achievement was re- 

 served for Newton, who proved that they were necessary results of 

 the law of universal gravitation." 



This sentence would have astonished Newton ! It places the cart 

 before the horse. From the empirical laws of Kepler the theory of 

 gravitation was mathematically derived by Newton. Not the re- 

 verse. What a confusion of ideas that Kepler's laws could both be 

 demonstrated mathematically and observed as facts ? How it be- 



