Air movements upon a larger scale are produced by the excessive warming in the tropics, 

 the expansion of lower layers of the atmosphere, the lifting of the upper layers and their 

 flow polewards, while the colder and heavier air to the north and south moves towards the 

 equator. Can you trace the transformation ? 



Seeing how the wind acquires its energy much interest attaches to the question of its 

 expenditure. Distribution of heat and moisture over the globe, destroying rocks and artificial 

 structures, the carrying and deposition of sand and dust, the production of water currents and 

 waves with all their effects about the shore, the transportation of pollen and seeds and the 

 assistance rendered in the distribution of plants and animals over the earth. Man may util- 

 ize the energy of the wind by means of windmills and in the case of sailing boats, balloons. 



2. RUNNING WATKR. The heat of the sun is communicated to bodies of water, driving 

 the molecules apart and causing it to become vapor. This vapor, mixed with air, is ligliter 

 than the air alone and rises, for the same reason that the warmed air does and gives rise to 

 winds. In thus rising it has mass kinetic energy and is acquiring mass potential with refer- 

 ence to sea level. In the cold upper regions it loses heat and condenses, forming clouds, Which 

 ma)' be shifted over the land by the winds. The minute drops of the clouds unite and start 

 to fall. Why? What transformation of energy now occurs? When the drops strike the 

 ground they instantly lose their kinetic energy, thus doing work upon the earth or receiving 

 a supply of heat. Being still above sea level they possess a certain amount of the mass 

 potential energy which they had in the clouds. When collected into a lakelet or stream of 

 water this potential energy may be converted into kinetic energy, in which fonn it is able to 

 accomplish work. 



The direct impact of the raindrops disintegrates and removes soil and recks, lowering the 

 general level of the land (ra'n erosion). In streams the water forms for itself a channel which 

 it deepens and widens. The material is transported towards the lake or sea, being tempo- 

 rarily deposited upon the way as flood plains, bars, cones, deltas, etc., and being finally spread 

 in sheets over the bed of the body of water into which it empties. Man may utilize this ener- 

 gy in transporting logs, rafts and boats, in turning fishing-wheels in the west, and various 

 forms of water-wheels. Trace the transformation of the energy in the case of the great 

 dynamos at Niagara, each dynamo being driven by a great water-wheel. 



3. MOVING ICE. A glacier or great continental ice-sheet possesses mass potential and 

 mass kinetic energy which has been acquired as in the preceding case, the only difference 

 being that the vapor is congealed into snow. This snow accumulates in favorable places and 

 by pressure and melting is compacted into ice. Owing to the attraction of gravitation this 

 ice slowly flows to a lower level. Trace this kinetic mass energy to its source. 



Glaciers expend their energy in making rock-basins, disrupting reck masses, in grinding 

 much of it into powder, in removing former soils, in transportation of rock debris, in forming 

 sheets of boulder clay, or "till," and in the making of moraines. One or more of these effects 

 may be seen nearly everywhere north of the Ohio and Missouri rivers. The melting of exten- 

 sive ice-sheets brought out from the ice much of the finer material and formed valley-trains, 

 sand plains and out-wash aprons of sand and gravel. Man has not attempted to utilize the 

 kinetic energy of glaciers. 



4. PLANT KNKRGY. The green coloring matter of plants (chlorophyll), using the Hglit 

 of the sun is able to separate the atoms in the molecules of carbon- dioxide gas, using the 

 carbon to make starch by uniting it with a certain amount of water and throwing away the 

 oxygen. Light is thus transformed into atomic kinetic and this into atomic potential energy, 

 which may be thought of as residing in the carbon. The carbon-dioxide gas ccines from the 

 air and by this process the green plants get the carbon needed for their tissues and the energy 

 which they must have for warmth and movement. This is to be thought of as a process of 

 feeding. The carbon is loosely united with hydrogen f?nd oxygen to make various plant prod- 

 ucts, but retains a certain amount of its atomic potential energy represented by its separation 

 from oxygen alone. These plant materials may be stored in the root, stem, leaf, fruit and 

 seed. 



When these plants desire to liberate and utilize some of this stored energy the gas oxygen 

 is taken into their tissues from the atmosphere (external respiration^). Certain molecules con- 

 taining carbon are broken down and this carbon unites with the oxygen forming carbon- 



