PRELUDE TO THE EPOCH OF GALILEO. 11 



nearly the same way as Varro, and in favour of 

 which a claim has been made 1 (I think an un- 

 founded one,) as if it contained the true principle 

 of this problem. The work is " Jordanus Nemo- 

 rarius De Ponder ositate" The date and history of 

 this author were probably even then unknown ; for 

 in 1599, Benedetti, correcting some of the errours 

 of Tartalea, says they are taken "a Jordano quo- 

 dam antiquo." The book was probably a kind of 

 school-book, and much used ; for an edition printed 

 at Frankfort, in 1533, is stated to be Cum gratia 

 et privilegio Imperially Petro Apiano mathematico 

 Ingolstadiano ad ccxx annos concesso. But this 

 edition does not contain the Inclined Plane. Though 

 those who compiled the work assert in words some- 

 thing like the inverse proportion of Weights and 

 their Velocities, they had not learnt at that time 

 how to apply this maxim to the Inclined Plane ; 

 nor were they ever able to render a sound reason 

 for it. In the edition of Venice, 1565, however, 

 such an application is attempted. The reasonings 

 are founded on the usual Aristotelian assumption, 

 "that bodies descend more quickly in proportion 

 as they are heavier." To this principle are added 

 some others ; as, that " a body is heavier in pro- 

 portion as it descends more directly to the center," 

 and that, in proportion as a body descends more 

 obliquely, the intercepted part of the direct descent 

 is smaller. By means of these principles, the " de- 



1 Mr. Drinkwater's Life of Galileo, in the Lib. Usef. Kn. p. 83. 



