xxvri -3 GENEKALISATION. 611 



error. It is truly difficult at the first moment to recognise 



iron SSS* be * Wee \ the g radual r ^ting of a piec^e O f 

 iron, and the rapid combustion of a heap of straw Yet 

 Lavoisier s chemical theory was founded upon the similarity 

 of tne oxydismg process in one case and the other WP 

 have only to divide the iron into excessively small particles 

 to discover that it is really the more combustible of the 

 two and that it actually takes fire spontaneously and burns 

 ike tinder. It is the excessive slowness of the process in 

 characf a maSS1Ve piece of iron which disguises its real 

 If Xenophon reports truly, Socrates was misled by not 

 making sufficient allowance for extreme differences of de- 

 gree and quantity. Anaxagoras held that the sun is a fire 

 but Socrates rejected this opinion, on the ground that we 

 can look at a fire, but not at the sun, and that plants grow 

 by sunshine while they are kiUed by fire. He also pointed 



cools f^ *?* 6ated ln a fiie 1S n0t luminous > and soon 

 cools, whereas the^sun ever remains equally luminous and 



' tl tA-T mistakes evidently arise from not perceiv- 

 ing that difference of quantity may be so extreme as to 

 assume the appearance of difference of quality. It is the 

 east creditable thing we know of Socrates, that after point 

 ing out these supposed mistakes of earlier philosophers, he 

 advised his foUowers not to study astronomy 



Masses of matter of very different size may be expected 

 to exhibit apparent differences of conduct, arising from the 

 various intensity of the forces brought into play. Sany 



ST T Ught - i1} re(luisite to ima S ine occulfc *>s 

 oducmg the suspension of the clouds, and there have even 



3n absurd theories representing cloud particles as minute 

 water-balloons buoyed up by the warm air within them 



it we have only to take proper account of the enormous 

 comparative resistance which the air opposes to the fall of 

 minute particles, to see that all cloud particles are probably 

 constantly fallmg through the air, but so slowly that there 

 is no apparent effect. Mineral matter again is always re- 

 garded as inert and incapable of spontaneous movement 

 we are struck by astonishment on observing in a powerful 

 microscope, that every kind of solid matter suspended in 



Memorabilia, iv. 7. 



K B 2 



