268 Mr. Exleys Application of 



sphere is invariably continued down to the centre itself, 

 where it terminates with the infinite force of Boscovich 

 repeated an infinite number of times. The direction 

 changes to the opposite one, per saltum, at the surface of 

 the sphere of repulsion : and why not? It is quite as easy 

 and more natural to conceive that it thus changes at once, 

 than that it is always changing continuously backward and 

 forward ; but, which is a matter of great moment, the con- 

 tinuity of the quantity and of the law of force remains 

 unbroken, preserving the delightful harmony of nature. 



The inductive philosophy requires and demands this 

 continuity in the law ; unless the contrary could be shown 

 in any instance, we have as much right to say that the law 

 of gravitation does not exist in the infinity of places where 

 no observations have been made, as to say it does not exist 

 in the sphere of repulsion, that important space in which che- 

 mistry and its connate sciences produce all their phenomena. 



Thus since the 1st principle as to attraction has long 

 been established completely, by induction, and beyond the 

 power of controversy, and since we know from facts that a 

 central repulsion exists, the same induction obliges us to 

 admit the same force in the sphere of repulsion, especially 

 as not a single instance of repulsion acting according to 

 any other law can be shewn to exist, as belonging to any 

 atom of matter. 



The 2nd principle is perfectly simple and natural, and is 

 established by means of the first principle and induction 

 from facts ; for it is known that atoms do differ from each 

 other, and the difference stated is in complete unison with the 

 first principle, and quite sufficient to furnish all the variety 

 of atoms yet observed, and an infinitely greater variety. 



The material will of course be allowed, and we readily 

 admit that the creator originally brought into existence, 

 according to number, weight and measure, a quantity of 

 every sort of atoms requisite for the purposes of his grand 

 design in the structure of the universe. 



Every variety of atoms may, according to the theory, be 

 assumed ; but to find what sorts really exist, phenomena 

 should direct the assumptions. 



In my ** New Theory of Physics," it was stated that 

 nature presents two classes of atoms ; the one comprehending 

 the elementary substances most generally known, such as. 



