392 THE ADDRESSES, LECTURES, ETC., OF 



our steam-engines, by our hydraulic accumulators, and by com- 

 pressed air. It is with reference to electricity in this form that I 

 propose to put certain experiments and explanations before you. 



Electricity, as you know, is the youngest form of energy with 

 which we are practically acquainted. Although the only available 

 source of that energy was until lately the galvanic battery, attempts 

 were made from the days of Yolta, at the beginning of the present 

 century, to apply that force for the obtaining and transmitting of 

 power. A very little consideration will convince us that all those 

 efforts must necessarily have been futile. A pound of zinc is pro- 

 duced by the combustion of from 15 to 20 pounds of coal, and 

 while a pound of coal in burning gives out 12,000 heat-units, a 

 pound of zinc in burning gives only 2,340. Thus zinc gives in 

 burning only one-fifth of the effect in energy that coal does, and 

 taking the cost of zinc at 50 times that of coal, it follows that the 

 cost of energy, in the case of a galvanic battery, is, roughly speak- 

 ing, 250 times greater than in a steam-boiler. Thus handicapped, 

 it was not likely that electricity could be made available for pro- 

 ducing powerful effects, although the attempts that were made 

 in ignorance of the laws of nature governing the force of electri- 

 city were numerous. 



Before entering upon the most essential part of my subject, I 

 must mention an invention or discovery of Seebeck in 1822 that 

 of the thermo-battery. I have here a thermo-battery in which 

 the heating agent is gas, which we will have lighted, and you 

 will see that from it proceeds a current, exceedingly weak, yet a 

 current which owes its origin entirely to heat ; and by it we can 

 effect transmutation, so to speak, of heat energy into electrical 

 energy, without any intermediate mechanism or contrivance. 

 If alternate strips of metal, of different positions in the thermo- 

 electrical scale, such as bismuth and antimony, are joined at the 

 ends into couples, and one point of juncture is heated, while the 

 next is kept cool, a current is set up, flowing from the hot to the 

 cold juncture, and the moving power of the current thus produced 

 is proportionate to the difference of temperature between the hot 

 juncture and the cold, and to the relative positions of the two 

 metals in the thermo-electric scale. If this transformation could 

 be effected without loss, we might hope that the thermo-battery 

 would be the ultimate and most perfect solution of the problem of 



