194 ELEMENTS OF GENERAL SCIENCE 



through the aid of the sun's energy, it is not difficult to see 

 that the sun is the ultimate source of energy for all the 

 activities of living things. In connection with the preceding 

 study of work and energy it is important that we consider 

 the relation of the earth and sun to other bodies which radi- 

 ate light and heat. However, since electricity and electrical 

 appliances occupy so large a place in the work and pleasures 

 of modern life, electricity and electrical work will be discussed 

 next, and then we shall consider some elementary questions 

 in astronomy. 





