30 ATTRACTION OF GRAVITATION. 



little oil between them to fill up the pores in their surfaces, 

 they will cohere so powerfully as to require a very consi- 

 derable force to separate them. Two globules of quicksil- 

 ver, placed very near to each other, will run together, and 

 drops of water will do the same. The ascent of water and 

 other liquids in sugar, sponge, and all porous bodies is a spe- 

 cies of this attraction, and is called capillary attraction. 



Some bodies appear to possess a power which is the re- 

 verse of the attraction of cohesion. It is called repulsion, 

 and is supposed to extend to a small distance around bodies, 

 so as to prevent them from coming into actual contact. 

 Water repels most bodies till they are wet. A small needle 

 carefully placed on water will float. The drops of dew 

 which appear in the morning on plants assume a globular 

 form, from the mutual attraction between the particles of 

 V4^ater; and upon examination it will be found that the drops 

 do not touch the leaves, for they roll off in compact bodies, 

 which would not be the case if there existed any degree of 

 attraction between the water and the leaf. The repelling 

 force between water and oil is so great that it is impossible- 

 to mix them in such a manner that they shall not separate 

 again. 



Questions. — 1. What is matter ? 2. What are the general pro- 

 perties of bodies ? 3. What is impenetrability ? 4. By what experi- 

 ments is this property of matter illustrated ? 5. Define extension and 

 figure. 6. What is divisibility, and liow illustrated ? 7, Define inert- 

 ness ? 8. What is meant by attraction ? 9. Attraction of cohesion ? 

 10. What is said of the attraction of solids and fluids ? 11. What ex- 

 periments illustrate cohesive attraction .' 12. What is capillary at- 

 traction.' 13. What is repulsion, and by what experiments illua- 

 Uftted. 



LESSON 16, 



Attraction of Gravitation. 



Roctilin'ear, consisting of right or straight lines. 

 Curvilin'ear, consisting of crooked, or curved lines. 

 Projec'tile, a body put in motion. 

 Evaga'tion, a wandering deviation. 

 Phenom'enon, (pi. phenomena) appearance^ commonly oxprossivc 

 of some remarkable appearance in nature. 



The attraction of gravitation is only a modification of the j 



