12 SCIENCE PRIMERS. [NATURE AND 



fall upon the man, and seriously hurt him. If that 

 happens it will be called an " accident, " and the man 

 will perhaps say that by " chance " he went out, and 

 then " chanced " to take refuge under the tree, and so 

 the " accident " happened. But there is neither chance 

 nor accident in the matter. The storm is the effect of 

 causes operating upon the atmosphere, perhaps hun- 

 dreds of miles away ; every vibration of a leaf is the 

 consequence of the mechanical force of the wind 

 acting on the surface exposed to it ; if the bough 

 breaks, it will do so in consequence of the relation 

 between its strength and the force of the wind ; if it 

 falls upon the man it will do so in consequence of the 

 action of other definite natural causes ; and the posi- 

 tion of the man under it is only the last term in a 

 series of causes and effects, which have followed one 

 another in natural order, from that cause, the effect of 

 which was his setting out, to that the effect of which 

 was his stepping under the tree. 



But, inasmuch as we are not wise enough to be able 

 to unravel all these long and complicated series of 

 causes and effects which lead \o the falling of the 

 branch upon the man, we call such an event an 

 accident. 



9. Laws of Nature ; Laws are not Causes. 



When we have made out by careful and repeated 

 observation that something is always the cause of a 

 certain effect, or that certain events always take place 

 in the same order, we speak of the truth thus dis- 

 covered as a law of nature. Thus it is a law of 

 nature that anything heavy falls to the ground if it is 



