IN NATURAL PHILOSOPHY. 9 



15. Why will water wet your hand while mercury will not? 

 Because in the former case there is an adhesion, in the 

 latter none. 



1 6 Why is a tub or pail liable to fall to pieces if not filled 

 with water or kept in the cellar? 



Because the moisture dries out of the pores, and the wood 

 shrinks so as to let the hoops fall off. 



17. Name instances where the attraction of adhesion h 

 stronger than that of cohesion. 



Wood fastened by glue will often split before the glue will 

 yield. Paper stuck with paste, and bricks with mortar, are also 

 examples. 



GRAVITATION. 



63. i. When an apple falls to the ground ^ how much does 

 the earth rise to meet it? 



The earth falls as much less distance than the apple, as its 

 weight is greater. 



2. What causes the sawdust in a mill-pond to collect in large 

 masses ? 



The attraction of gravity which exists between all bodies, 

 whereby they attract each other. All bodies on the earth 

 would tend to approach each other, and the big ones would 

 gather all the little ones around them were they as free to move 

 as the sawdust floating on water. 



3. Will a body weigh more in a valley than on a mountain f 

 It will, because the attraction of the earth is greater. 



4. Will a pound weight fall more slowly than a two-pound 

 weight ? 



They will both fall in the same time, except the slight 

 difference which is caused by the resistance of the air. Galileo 

 propounded this view and proved it, in the presence of a vast 

 crowd, by letting unequal weights fall from the leaning tower 

 of Pisa. 



