418 LAWS OF MOTION. 



those motions are objects which, in their nature- 

 are altogether separate and distinct ; the motion? 

 of the index may be caused by the elasticity of 

 steel, as in a watch ; or by the density and 

 weight of a piece of iron, as in a clock. The 

 science, however, which treats of the one, is 

 entirely separate and distinct from the other. 

 The same difference prevails with respect to 

 astronomy; while the motions which the various 

 planets describe, are mechanical effects, the 

 cause of these motions is a physical one; while 

 the science of mathematics is the means by 

 which different distances and motions, numbers 

 and magnitudes, are measured and ascertainedj 

 the science of physics, on the contrary, is con- 

 versant with the nature of the causes, by which 

 those motions are produced ; it explores the 

 essential properties of matter ; it distinguishes 

 the separate attributes of each ; it ascertains 

 the nature of the active, the aptitude and 

 capacity of the passive ; the power in the one 

 of overcomingthe resistance of the other; while 

 mathematics are merely conversant with effects, 

 physics, on the contrary, investigate the nature 

 of came. The causes of natural phenomena are 

 not to be discovered by mathematical rules, al- 

 though the effects may be ascertained by them.* 







* I recollect to have seen it observed by some one, that if 

 any one were to attempt to prove by algebra, how it is that 

 fire burns ; to explain the nature and operation of the sun by 



