36 GKAVITATION. 



at another, you get the inverse accordingly. So 

 it is as regards the attraction of these two balls, 

 they attract according to the square of the 

 distance, inversely. I want you to try and 

 remember these words, and then you will be 

 able to go into all the calculations of astrono- 

 mers as to the planets and other bodies, and tell 

 why they move so fast, and why they go round 

 the sun without falling into it, and be prepared 

 to enter upon many other interesting inquiries 

 of the like nature. 



Let us now leave this subject which I have 

 written upon the board under the word FOECE 

 GTKAVITATION and go a step further. All 

 bodies attract each other at sensible distances. 

 I showed you the electric attraction on the last 

 occasion (though I did not call it so); that 

 attracts at a distance; and in order to make our 

 progress a little more gradual, suppose I take a 

 few iron particles [dropping some small frag- 

 ments of iron on the table]. There, I have 

 already told you that in all cases where bodies 

 fall, it is the particles that are attracted. You 

 may consider these then as separate particles 

 magnified, so as to be evident to your sight ; 

 they are loose from each other they all gravi- 



