Energy. 321 



The simple weight of water pressing vertically upon a turbine wheel 

 hung in a vertical tunnel, causes the wheel with its shaft to revolve 

 horizontally. Bevel gearing attached to the vertical shaft enables the 

 motion to be transferred to a horizontal shaft, and a crank attached to 

 this, gives vertical movement to a saw or a gang of saws. Other ad- 

 justments of gearing slowly push a log endwise against the saws, which, 

 by tearing out particles of the timber against their cohesion, finally 

 leave the log split up into boards. The molar motion of the water is 

 thus transformed from a vertical rush to a horizontal whirl, in a part of 

 the machinery, then to a vertical roll, then a vertical vibration, 'and is 

 at last converted from molar movement to molecular motion, in the in- 

 creased heat of the surrounding atmosphere, and in the machinery, the 

 boards and the sawdust, and so disappears from observation. In this 

 example we have several forms of motion, slow and fast, one part of 

 the machinery going with lightning rapidity, other parts with deliberate 

 slowness ; some moving with a rotary vertical, others with a rotary hor- 

 izontal motion; some with a right line horizontal movement, others with 

 violent vertical vibrations. The machinery itself is of various materials 

 arranged in a variety of forms. It is, in fact, obvious that the variety 

 of forms the motion takes in passing from one part of the machinery to 

 another is altogether due to these various forms, materials and arrange- 

 ments of the machinery itself. If the journals were square instead of 

 round the shafts would never revolve ; if a single cog were missing 

 from any of the cog gearing the saw would never go ; if the saw were 

 made of wood instead of steel, its work would very speedily terminate; 

 if the lubricating oil were allowed to disappear from the bearings for a 

 few hours, the energy arrested and converted into heat at the points of 

 friction, would probably soon reduce the greater part of the mill to car- 

 bonic dioxide. The proper result is therefore obtained only by the 

 operation of the energy upon a machine of particular form and adjust- 

 ment. From the same shaft that runs the saw, a belt might be made 

 to convey motive force to a printing press, a loom, a lathe, an electric 

 dynamo, or any one of a thousand machines of a different form and ac- 

 complishing a different result. Starting with the water in a position of 

 potential energy above the mill dam, we trace this energy converted in- 

 to molar motion in the whirl of shafts and wheels to its final dissipation 

 in molecular motion mostly heat mostly, but not wholly. In the 

 case of the dynamo, if it is operated for illuminating, it ought to be 

 mostly light ; if the dynamo runs the street cars the energy becomes 

 work again before it disappears as heat. Some of it reaches us in the 

 shape o^ sound, in the hum, whirl and crash of the different parts of 

 the machinery. If we should stand in glass slippers, or even rubber 

 ones, near one of the rubber driving belts used in the mills for convey- 



