16 GRAVITATION. 



possesses it, that there is never any change in 

 the quantity of it ; and, first of all, I will take 

 as illustration a piece of marble. Now this 

 marble has weight as you will see if I put it 

 in these scales; it weighs the balance down, 

 and if I take it off, the balance goes back again 

 and resumes its equilibrium. I can decompose 

 this marble and change it, in the same manner 

 as I can change ice into water and water into 

 steam. I can convert a part of it into its own 

 steam easily, and show you that this steam from 

 the marble has the property of remaining in the 

 same place at common temperatures, which 

 water-steam has not. If I add a little liquid to 

 the marble and decompose it( 6 ), I get that which 

 you see [the Lecturer here put several lumps 

 of marble into a glass jar, and poured water and 

 then acid over them ; the carbonic acid imme- 

 diately commenced to escape with considerable 

 effervescence] the appearance of boiling, 

 which is only the separation of one part of 

 the marble from another. Now this [marble] 

 steam, and that [water] steam, and all other 

 steams gravitate just like any other substance 

 does ; they all are attracted the one towards the 

 other, and all fall towards the earth, and what 



