SEQUEL TO THE EPOCH OF GALILEO. 55 



troversy respecting the truth of the Copernican 

 System; for this law supplied the true answer to 

 the most formidable of the objections against the 

 motion of the earth ; namely, that if the earth were 

 moving, bodies which were dropt from an elevated 

 object would be left behind by the place from which 

 they fell. This argument was reproduced in various 

 forms by the opponents of the new doctrine ; and 

 the answers to the argument, though they belong 

 to the history of Astronomy, and form part of the 

 Sequel to the Epoch of Copernicus, belong more 

 peculiarly to the history of Mechanics, and are 

 events in the sequel to the Discoveries of Galileo. 

 So far, indeed, as the mechanical controversy was 

 concerned, the advocates of the Second Law of 

 Motion appealed, very triumphantly, to experiment. 

 Gassendi made many experiments on this subject 

 publicly, of which an account is given in his Epis- 

 tolw tres de Motu Impresso a Motor e Translator 

 It appeared in these experiments, that bodies let 

 fall downwards, or cast upwards, forwards, or back- 

 wards, from a ship, or chariot, or man, whether at 

 rest, or in any degree of motion, had always the 

 same motion relatively to the motor. In the appli- 

 cation of this principle to the system of the world, 

 indeed, Gassendi and other philosophers of his time 

 were greatly hampered; for the deference which 

 religious scruples required, did not allow them to 

 say that the earth really moved, but only that the 



J iM.mt. ii. W). 



