54 ANDREW JACKSON HOWE. 



Light has been denominated an energy, and not 

 an ethereal substance. It may be transformed into 

 heat and electrical units, it may assume two or three 

 kinds of energy. The sun is the great source of light 

 in its own system, but looked at from Sirius its twinkle 

 becomes a star of the fourth or fifth magnitude. The 

 vivifying powers of solar energy are all important to 

 our planet. Without the influence of light and heat 

 the earth would have no seasons, no plants, no animals, 

 no rains, no atmosphere, no condition contributing to 

 the support of life. In shaded places poisonous fungi 

 may vegetate, and in the deeper parts of the sea where 

 heat does not reach, nor solar rays penetrate, there may 

 be encountered organic forms, both floral and fauna], 

 but their support is borrowed from material that lias 

 been under the sun's influence. Near the poles the 

 water swarms with marine life, but the water is rich 

 in protoplasm that has been developed under the en- 

 ergies of a tropical sun. The energizing influences of 

 solar rays are stored in trees, and eventually laid away 

 in coal banks, hence their character should be con- 

 sidered in the economies of our planet. 



POTENTIAL AND KINETIC ENERGIES. 



In a discussion of matter, power, and motion, it 

 became necessary to allude to the forces inherent in 

 stellar bodies, and as displayed in the movements of 

 atoms, molecules, and masses. It is perhaps unfortu- 

 nate and to be regretted that scientists have not formu- 

 lated better terms for the two activities which forever 

 exert antagonistic qualities, as gravitation and repul- 

 sion ; but we must become familiar with the language 

 of science, if we would understand its teachings. A 

 potential energy may abide or continue in a state of 



