58G Transactions of the American Institute. 



ments, you will see the cause of the apparent increase of power. 

 An ox can drag four wheelbarrows as well as one. Hitch four baby-carts 

 to a horse, and you will not see any signs of weakness. Mr. High- 

 ton used a very strong battery ; and hence, when you put on the addi- 

 tional electro-magnets, with twice the length and twice the thickness 

 of wire, he produced apparently a greater force. Yet he does not 

 get the same force from each additional magnet. There is a limit to it. 



The question arises, what are the conditions under which the great- 

 est power will be evolved by any galvanic circuit? If a water-wheel 

 turns with the velocity of the stream, it gives no 'power ; if it stands 

 still, it does no work. The law is, that it does the greatest work 

 when it moves with one-half the velocity of the water. So the gal- 

 vanic battery does the most work when the work outside is equal to 

 the work inside, i. e., the resistance of the wire must be equal to one- 

 half the maximum powder of the battery ; or the resistance in the coil 

 should be equal to the resistance in the liquid. 



Of the success of the electro-magnetic engine, I have no doubt ; 

 but when we consider its economy as compared with steam, we mnst 

 remember that in the steam-engine we burn carbon, a substance having a 

 very low chemical equivalent, whereas, in the voltaic engine we bum 

 zinc, a substance having a high chemical equivalent. It takes more 

 than thirty-two puunds of zinc to do the work of six pounds of car- 

 bon. Moreover, the six pounds of carbon are raised to such a height 

 that they fall twice as far — i. e., each equivalent of carbon combines 

 with two equivalents of oxygen, wdiereas, zinc combines with but 

 one ; so that the proportion is as eleven to one in favor of carbon. 

 But, taking the market value into consideration, the difference is 

 vastly greater, for zinc costs $320 a ton. 



The President — The cost of the power is about twenty-five times 

 that of steam power. 



Dr. Van der Weyde — For oxidizing zinc we are obliged to use an 

 acid which costs money. For oxidizing coal we use air, which costs 

 nothing. 



Mr. J. K. Fisher — The cost of the zinc will not amount to anything, 

 for we can sell the zinc paint for more than the zinc costs. 



Dr. Yan der Weyde — Experiments which I tried, thoroughly, many 

 years ago, the apparatus for which is still in this building, fortified 

 the position taken to-night by Prof. Phin. I commenced in Holland, 

 in 1838 or 1839, to make an electro-magnetic engine to turn my lathe 

 with. It did the work successfully, but it consumed a tremendous 

 amount of zinc. About tw r o years ago, a gentleman by the name of 



