dioxide gas again (internal respiration^. The potential atomic energy is first converted into 

 kinetic atomic, as the atoms rush together, and this energy in turn is transformed into heat, 

 or mass kinetic for the use of the plant. Plantsylrtf' in order to get materials for their tissues 

 and also to get energy. They breathe in order to liberate energy which they already possess. 

 Man may make use of the energy contained in plant tissue, such as wood, leaves, straw, moss, 

 vegetable oils, resins, etc. When brought 10 a suitable temperature the carbon bearing mole- 

 cules disintegrate, charring takes place, and the carbon unites with the oxygen of the atmosphere 

 liberating heat. This heat is transformed sunlight. Many substances derived from plants, as 

 alcohol, peat, coal, petroleum, natural gas, etc., still retain much of the plant's original poten- 

 tial energy, which may be set free and liberated as heat. Consider the transformations of 

 energy that have taken place in our stoves, paraffin candles, kerosene lamps, artificial gas, 

 machinery operated by steam engines. Plants without chorophyll must get their energy just 

 as do animals to be now described. 



5. ANIMAL ENERGY. By a process of feeding, either directly or indirectly, animals take 

 into their bodies those substances which have b^en manufactured by plants; chiefly starches, 

 sugars, oils and gums. These contain carbon with its supply of potential atomic energy, 

 representing so much transformed sunlight. Plants without chlorophyll must secure their 

 energy in the same way. Animals feed in order to get materials for their tissues and to get 

 their necessary supply of energy. Plant products are worked over into animal substances, of 

 which carbon is the chief ingredient (assimilation). 



All animals must have energy available for heat and movement, and in exceptional cases 

 for sound, light and electricity. Certain molecules are broken down enabling the carbon to 

 unite with oxygen, brought in by the process of iesp iratiou , thus setting free the energy that 

 was potential. In the case of the oils, hydrogen also is /available for similar union with 

 oxygen, forming wafer and liberating energy. Animals respire in order to liberate energy. 

 What animal energies may man directly utilize ? Can you trace the transformations of 

 energy from the light of a tallow candle back to the sun ? 



The "self-sustaining aquarium," a valuable adjunct of every schoolroom and home, can 

 now be readily understood. It contains green plants and animal life so adjusted that the 

 water does not need to be changed. Small quantities of food are periodically given the 

 animals, thus supplying them with matter and energy. The oxygen dissolved in the water 

 unites with the carbon of the animal substance, forming carbon dioxide gas and setting free 

 the energy. The carbon-dioxide gas is supplied the water and taken up by the plants. Us- 

 ing the light of the sun, this gas is separated into carbon and oxygen. The carbon is 

 retained by the plant for its own use while the oxygen is thrown into the water again for the 

 ue of the animal life. Note that you supply the animal life with matter and energy, the 

 carbon being passed over to the plant which is thus enabled to get a much needed material 

 for its tissues and at the same time secure energy from the sun. 



6. ENERGY NOT FROM THE SUN. In all the above cases the sun has been shown to be 

 the source of energy. Where could it have gotten its tremendous supply ? Can it last 

 forever? In addition to the above we have other great manifestations of energy, which can 

 not be traced directly to our present sun. The earth is moving forward in its orbit about the 

 sun at the rate of about 18 miles a second, bringing us the change of seasons. It is rotating 

 upon its axis at a maximum rate of over 17 miles a minute, causing the changes of day and 

 night, influencing the oceanic and atmospheric currents, and causing the tidal waves. In 

 addition to this mass kinetic energy, the outer crust possesses a great quantity of mass 

 potential energy with reference to the interior, giving rise to subsidence in places and up- 

 heavals in others, often with accompanying earthquakes. The earth possesses a tremendous 

 store of internal heat, causing volcanoes, geysers and hot springs. Minerals occur in the 

 earth, such as iron, sulphur, etc., which have an attraction for oxygen and hence they 

 possess atomic potential energy. According to the Nebular Theory of the origin of our earth 

 all these forms of energy were derived from what constituted the sun at the time that the 

 earth was separated from it. According to the other two theories of earth origin this energy 

 came from outside our present solar system. 



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