EVOLUTION AND T/lEISAf. 387 



a parabolic curve a cannon-shot fired obliquely into the air, and 

 extended the same conception to the orbital revolution of the 

 earth and other planets round the sun, he perceived that even 

 lhe.se were only cases of the still more general fact, that all 

 material bodies attract one another with forces proportional to 

 their respective masses, and inversely as the squares of their 

 distances, which expression is known as the law of Universal 

 (iravitation. Now the attributing this general fact to a universal 

 property of mutual attraction inherent in every particle of matter, 

 is really but another mode of expressing the same thing, a mere 

 figure of speech, which no more accounts for the phenomenon, 

 than does its similarity to any number of other phenomena. 



Let me illustrate this by reference to a &quot; property &quot; which is 

 not universal. I might place before you two bars of iron, exactly 

 resembling one another in every particular of which our senses 

 can directly inform us, such as size, weight, external aspect, and 

 internal texture, as shown by fracture ; and yet one of them, 

 under certain conditions, exerts powers of which the other shows 

 itself to be altogether destitute. When brought near to a piece 

 of iron, it draws it to itself with a force of which we become 

 conscious in endeavouring to resist it ; and even from a consider 

 able distance it deflects a compass-needle from its true position, 

 in a manner altogether dissimilar to that which happens when 

 the other bar is brought near it. From observation of these facts, 

 I can predict that if both these bars be buoyed up so as to float 

 on water, one of them will soon settle itself in a north and south 

 direction, and will return to that direction whenever deflected 

 from it ; while the other will remain in any position in which it 

 may be placed. And I distinguish the former as having &quot;mag 

 netic properties&quot; of which the latter is destitute. Further, my 

 knowledge of the laws of magnetic science enables me to predict 

 that by moving the magnetic bar in a particular manner over the 

 non-magnetic bar, I can render the latter also magnetic, or, as 

 may be said, can impart magnetic properties to it ; but as this 

 cannot be done to a bar of gold or silver, copper or lead, we say 

 that iron is distinguished from metals generally by its capacity 

 for being magnetized. Now, this is clearly no explanation of the 

 phenomena which we trace to the action of magnetic force ; it 



