ELECTRO-MOTIVE ENGINES 225 



20 square feet of platinum would produce power equivalent to one horse ; and the 

 vessel wont at the rate of four miles an hour. In 1839, Jacobi tried another experi- 

 ment, with a battery of 64 platinum plates, each having 36 square inches of surface ; 

 when the boat, with a party of 14 persons on board, went against the stream at the 

 rate of three miles an hour. 



In 1837, Mr. Thomas Davenport, of the United States, constructed a rotary engine, 

 in which permanent and electro-magnets were employed. Mr. Taylor, in 1839, 

 patented an electro-magnetic engine, both in America and in this country, the prin- 

 cipal novelty in which was, that instead of changing the poles of the magnets, the 

 electric action was, at fixed rapid intervals, entirely suspended. In 1837, Mr. David- 

 sou, of Edinburgh, constructed an engine, in which he produced motion by simply 

 suspending the magnetism, without a change of the poles. Mr. Robert Davidson 

 placed an electro-magnetic locomotive on the Edinburgh and Glasgow Railway ; the 

 carriage was 16 feet long and 6 feet broad, and weighed about 5 tons. All tho 

 arrangements appear to have been very complete, but when put in motion on the 

 rails, it was not possible to obtain a greater speed than four miles an hour. 



Professor Page's electro-magnetic engine was for some time looked upon as a 

 triumph. The fundamental principle of it is thus described: 'It is well known 

 that when a helix of suitable power is connected with the poles of a battery in action, 

 an iron bar, within it, will remain held up by the induced magnetism, although the 

 helix be placed in a vertical position ; and if the bar is partly drawn out of the helix 

 by the hand, it goes back with a spring, when the hand lets go its hold. This power 

 the action of the helix upon the metallic bar within it is the power used in Pago's 

 engine.' Professor Page exhibited one of his engines, of between 4 and 5 horse- 

 power, at the Smithsonian Institution ; the battery to operate with being contained 

 within a space of 3 cubic feet. It was a reciprocating engine of 2-feet stroke, and 

 the whole, including the battery, weighed about one ton. Professor Page stated that 

 the consumption of 3 Ibs. of zinc per day would produce one horse-power. This 

 statement requires further investigation. 



Many similar attempts have been made to construct effective machines to be 

 moved by the power of the voltaic battery. Among others, Mr. Henley constructed 

 an electro-magnetic engine of considerable power for Mr. Talbot, and another for 

 Professor Wheatstone. In these . there were many ingenious mechanical arrange- 

 ments, invented to overcome some of the difficulties hitherto encountered ; but the 

 physical conditions were similar to those already described. Mr. Talbot's engine 

 was 3 ft. 6 ins. long, and 2 ft. 6 ins. wide ; when excited by a Grove's battery, con- 

 sisting of four cells with double plates of zinc, 9 ins. by 6 ins., platinum plates 9 ins. 

 by 65 ins., excited by diluted sulphuric acid in the proportions of 1 to 4, and concen- 

 trated nitric acid, it drove a lathe, with which was turned a gun-metal pulley, 5 ins. 

 in diameter ; but in three quarters of an hour the battery was quite exhausted. 



Mr. Hjo'rth, a few years since, exhibited in London a large machine, constructed 

 somewhat on the principle of Page's ; this, however, failed to produce any great me- 

 chanical effect, and it appears to have been abandoned. Dr. Lardner stated, in 1851, 

 that M. Gustavo Froment, of Paris, was using, with much advantage, an electro-mag- 

 netic engine in his workshops for turning lathes, planing machines, &c. Its use, 

 however, appears to have been abandoned, on account of the great cost of the battery 

 power. 



Hankel and Fessel, on tho Continent, the Rev. James William M'Gauley, Dr. 

 Kemp, and others, in Great Britain, have, at different times, excited much attention 

 by the ingenious machines which they have constructed. 



Notwithstanding these numeroiis trials, and, connected with them, an almost infinite 

 amount of experiment, it does not appear that any satisfactory explanation has ever 

 been given of the causes which have led to the abandonment of the idea of employing 

 electricity as a motive power. It was mainly with the view of directing attention to 

 these causes, that the essay read was written. 



Electro-magnetism undoubtedly affords an almost unlimited power. An electro- 

 magnet may be constructed which shall have a lifting power equal to many tons. It 

 is probable, that there are limits beyond which it would not be possible to increase the 

 power of electro-magnets ; those limits have not yet been reached ; but supposing them 

 to be attained, there is nothing to prevent the multiplying of the number of electro- 

 magnets in the arrangements. It may be stated, in connection with this part of the 

 subject, that from experiments made with Hoarder's magnetometer, it appears that the 

 development of magnetism in iron observes some special peculiarities. These may be 

 thus stated : "With the same electro-magnet there is, as the voltaic pairs in the battery 

 are increased, a gradual increase of magnetic force. With from one to seven elements 

 there appears an average excess of 31 Ibs. ; after this point, with the increase of battery 

 power, by the addition of pair after pair of zinc and platinum elejuents, the production 



