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to do work, or to overcome resistance. It can not be conceived of independently of matter 

 but adds nothing to its weight. It does not occupy space and hence is not matter. Kvery 

 conceivable activity in the universe takes place because the matter involved possesses energy 

 in some form. Without it all matter would be absolutely cold, dark and lifeless. Energy 

 cannot be destroyed by any finite power and neither can it be created. Either it has always 

 existed or else it was created by DKITV. It can easily be made to undergo many transforma- 

 tions without any actual loss. The following varieties of energy are recognized: 



1. KINETIC ENERGY. This is possessed by all masses of matter which are in motion. 

 We may recognize mass kinetic, molecular kinetic and atomic kinetic energy. This energy 

 must have been communicated to the moving particles from some outside source. 



2. POTENTIAL ENERGY. This results from the relative position of bodies that have a 

 mutual attraction for one another, as gravitation, cohesion or chemical affinity. If separate 

 and free to move they will acquire motion and their potential energy will be gradually trans- 

 formed into kinetic. Analyze the transformations in the case of a ball thrown vertically into 

 the air; in the case of a swinging pendulum. Find other illustrations. We may recognize 

 mass potential, molecular potential and atomic, or chemical potential. In the case of a bent 

 bow or a compressed spring, the molecules are forced from their natural positions and will 

 return when permitted. The atoms of carbon and oxygen, under favorable conditions, 'will 

 rush together and form molecules of carbon-dioxide gas. 



3. HEAT. This is a form of energy that we know only as a wave motion, transmitted 

 through the mysterious medium known as the ether, which fills all space and penetrates all 

 other matter. The molecules of ether may communicate their movements directly to those of 

 other substances, or they may be made to vibrate by other means, as a blow. The faster the 

 molecules of the body vibrate the higher is the temperature. 



4. LIGHT. This is also a wave motion in the ether but a different type of energy from 

 heat. They may differ possibly only in their wave lengths. Some bodies allow light waves 

 to pass through them and are transparent. In opaque bodies the motion of the ether particles 

 is communicated to their molecules and the light energy is thus transformed into heat. In 

 green plants the light energy forces apart the atoms of carbon and oxygen in the molecules of 

 carbon-dioxide gas. Give the transformations. 



5. SOUND. This is a form of energy which manifests itself as a wave motion in the 

 molecules of air. Trace the transformations in some musical instrument. In thinking of heat, 

 light and sound we naturally think of their physiological effects, the impressions made upon 

 our sense organs and our minds, instead of the physical effects noted. Besides these ether 

 and air waves which we are able to perceive, a far greater number exist, known to us only 

 by experiment. 



6. ELECTRICAL ENERGY. In this we have a type of energy that has thus far defied all 

 attempts to discover its real nature. That it manifests itself as a form of motion seems very 

 probable, resident possibly in the "electrons'" of which the atoms thems.lves are now conceived 

 to be composed. Much of the industrial development of the present day is based upon the 

 conversion of other forms of energy into electrical energy by means of the dynamo. Any 

 material agent possessing energy, or having the property of attraction or repul.-ion, may 

 impart motion to other bodies and may be called a force. Gravitation, cohesion, chemical 

 affinity and magnetism are forces resulting from the properties of matter in which they reside. 

 Wind, running water and moving ice are forces in consequence of their mass kinetic energy. 



C. Nature's Forces. 



i. WIND. The sun's heat is communicated to the earth giving it molecular kinetic 

 energy, and this warms the adjacent air, pushing its molecules farther apart and 

 making it lighter. This mass of air now rises, being pushed up by the surrounding 

 heavier air, which descends to take its place. Why ? The mass potential energy of the colder 

 air is converted into mass kinetic, which is simply transferred to the warmer, lighter air 

 causing it to ascend. As it rises it gradually acquires mass potential energy with reference 

 to the surface of the earth. This air in motion, particularly the horizontal currents, with 

 its heat and kinetic energy constitutes the wind. Explain a lake, or sea breeze, by means 

 of a diagram. At night the water is warmer than the land and gives rise to a land breeze. 



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