20 



JUNIOR GRADE SCIENCE 



cubic inches or cubic centimetres could be thus found. Or, we could 

 get a glass measure having cubic inches or cubic centimetres marked 

 upon it, and pour the displaced water into it. But the best plan of all 

 is to use a vessel having cubic centimetres marked upon it. Water 

 can be put in such a vessel up to a certain mark, and the number of 

 cubic centimetres of water displaced by the solid can be seen at once 

 by noticing the number of divisions between the levels of the water 

 before and after the solid is put in. 



10. VOLUME OF PRISMS AND CYLINDERS. 



Simple application of volume measurement. The student cannot 

 have failed to notice that the 



volume of a cube =area of the base x height. 



The volume of any rectangular block, or of a cylinder, can be calculated 

 by the application of the same rule. This can be easily understood 



FIG. 19. To illustrate how the volumes of bodies having the same sectional 

 area all the way up are determined by multiplying the area of the base by the 

 height. 



by referring to the accompanying diagrams (Fig. 19, A), which may 

 be taken to represent solids divided into slabs one centimetre thick, 

 while the lowest slab of each block illustrated is divided into small 

 cubes representing cubic centimetres. The number of cubic centi- 

 metres in the bottom slab of each solid is evidentlv the same as the 



