92 THE ANATOMY OF SCIENCE 



opponents will not say that it is greater, for 

 they profess the contrary, and I also am of 

 their opinion: smaller it cannot be, since we 

 took the smallest weight that can exist: there 

 remains then only the case that the two are 

 equal, which I undertook to prove." This 

 learned physician was furnishing the sort of 

 proof which was in vogue in his day. If we 

 accept his conclusions without accepting his 

 demonstration, it would be a precedent which 

 we may often follow profitably with respect to 

 the many demonstrations which follow the fash- 

 ion of our owa age. 



Let us proceed to another stage in the sophis- 

 tication of mechanics, and look at the extremely 

 ingenious demonstration of the properties of the 

 inclined plane as given by Stevinus in 1605. 

 Figure 16 reproduces the frontispiece of his 

 book and illustrates his theorem that if two in- 

 clined planes have a common base, and one plane 

 is twice as long as the other, one body on the 

 shorter plane will pull as strongly as two such 

 bodies on the longer plane. The chain of balls 

 represented in the figure will not, he says, start 

 to go round, for, since conditions entirely simi- 

 lar to the original one would be constantly re- 

 peated, if it should move at all it would move 



