90 TRAXSACTIOXS OF TH K [DEC. 21, 



In short it possesses — 



Facility of distribution; 



Indefinitely great divisibility according to need; and 



The ability to concentrate great power in a very small space. 



I must limit myself, because of the brief time allotted, to the 

 consideration of a small part of my subject, and even in this I 

 will still further limit myself to phenomena occurring on so 

 considerable a scale as to be generally called engineering prob- 

 lems. 



I will particularly call your attention to the conversion and 

 reconversion of electrical energy into other forms of energy, in 

 three ways. 



First. — The conversion of heat into electrical energy. 



Second. — The conversion of electrical energy into light. 



Tliird. — The conversion of electrical energy into mechanical 

 •energy. 



The Conversion of Heat into Electrical Power. 



The direct conversion of heat into electrical energy, has already 

 had a partially successful, but not economical solution in Cla- 

 anond's stoves. 



According to Cabanellas, a Clamond's stove consisting of 6,000 

 elements and burning 23 lbs. of coke per hour, will give a current 

 of 218 volts difference of potential, and 7 amperes. 



Cabanellas also states that the amount of light obtained was 

 equal to about 560 standard English candles. 



This would give us nearly 20 candles per pound of coke. As 

 we shall presently see, this is a result much less economical of 

 fuel than can be obtained by the use of an engine and dynamo, 

 under very unfavorable circumstances. The liability to derange- 

 ment, and the first cost of Clamond's Pile, have prevented it from 

 becoming commercially successful. 



Those of you who are familiar with electrical terms will 

 pardon me if I devote a small portion of our time to the 

 endeavor to make their meaning clear to those who have given 

 little time or thought to them, but are familiar with jiurely 

 mechanical ideas. 



The ohm, volt, and ampere are the practical British Associa- 

 tion units used by electricians. 



The legal ohm is the resistance of a column of mercury one 

 square millimetre in cross section, and 106 centimetres in length, 

 at the temperature of melting ice. 



Ohm's law is 



T i. -L e nf L Diff. of Potential t E 



Intensity of Current= — ■. ,or 1=—, 



liesistance K 



from which you at once see that the resistance equals the ratio 



