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experiment was shown in which chemical action produced a current 

 of electricity ; this current was made to raise a weight, and the 

 same amoimt of electricity decomposed water into its two con- 

 stituents, hydrogen and oxygen. 



Energy is indestructible, although it may be transformed into 

 various modes of action, — mechanical energy, radiant energy, 

 electricity, chemical energy, &c. Coal, by the heat it evolves, is 

 able to generate mechanical effect. The energy of coal again is 

 derived from the sim, for in byegone ages the energy of the sun's 

 rays was stored up in vegetables, and these subsequently became 

 converted into coal. The " head of water " is clearly traceable to 

 the same source — water is raised by the sun in a state of vapour, 

 clouds are formed, and rain falls upon hills and high ground. 

 Here is a raised weight. The energy of the tides is not from the 

 same source. 



The Lecturer mentioned five methods of transmitting power : 

 (1) man, (2) ropes, (3) water, (4) air, and (5) electricity. 



Alan's work is usually directive. It is only when very large 

 numbers of men are employed that their work is at all efficient. 

 Most of the potential energy of man's food is converted into heat 

 of low temperature. 



Ropes which run on pulleys fixed on the ground are sometimes 

 used in Germany. But there is much friction, and, as a source of 

 power, the method is costly. 



Water is an agent much more frequently employed. It is 

 dammed up where it is required, and the fall of the water is the 

 source of the energy. The cliief advantage of water lies in its 

 incompressibility, hence, any pressure can be transmitted, and there 

 is no danger of an explosion. In mountainous districts it is cheap 

 and largely used. In Hull there is a "Water Company which 

 supplies water at a pressure of 7001bs. to tlie square inch. The 

 disadvantages of water are the friction which is set up where it has 

 to be sent to long distances, and the strain to which pipes are 

 subjected with every variation of pressure. 



Air is used in the air-break by Avliich a train is brought to a 

 standstill, and as compressed air in excavating tunnels and in 

 driving tramcars. Its disadvantage lies in its compressibility — 



