SCIENCE OF COMMON THINGS. 10 



How trees grow. Weight. * 



line directed from the centre of gravity is caused to fall within the base of the 



tree? 



Nature causes the various limbs to shoot out and 

 grow from the sides with as much exactness, in respect 

 to keeping the centre of gravity within the base, as 

 though they had been all arranged artificially. Each 

 limb growsj in respect to all the others, in such a man- 

 ner as to preserve a due balance between the whole. / 



CHAPTEK III. 



"WEIGHT. 

 1O8 What is weight f 



Weight is the measure of the attraction of gravita- 

 tion, or, in other words, it is the measure of force with 

 which a body^ is attracted by the earth. Iti an ordi- 

 nary sense it is the quantity of matter contained in a 

 body, as ascertained by the balance. 



1O0 To what is the weight of a tody proportional f 



The weight of a body is always proportional to the 

 quantity of matter contained in it. 



110 Why witt a ball of kad weigh more than a baU of cotton of the 

 same size ? 



Because the quantity of matter contained in the ball 

 of lead is much greater than the quantity of matter 

 contained in the ball of cotton. The attraction of gra- 

 vitation being proportioned to the quantity of matter, 

 it follows that the lead ball will be drawn towards the 

 earth with a greater force (i. e. will weigh more) than 

 the ball of cotton. 



111 A man of moderate weight upon the surface of the earth would 

 weigh two tons if transported to the surface of the sun : why would he weigh 

 more upon the surface of the sun than upon the surface of the earth f 



