106 ANNUAL OF SCIENTIFIC DISCOVERY. 



power than it had been before for one fifth of a horse-power, in a 

 smaller engine. A great variety of experiments were made with this 

 engine, until finally, by little daily increments, I obtained, by a trifling 

 addition of battery, a full two horse-power. By way of giving prac- 

 tical character to this engine, it was geared to a circular saw ten inches 

 in diameter, a turning-lathe, and grindstone, all of which it worked 

 simultaneously. After many satisfactory trials with this engine, it 

 was taken down, and all its available parts used in the construction of 

 a single horizontal engine, which was exhibited before the Smithso- 

 nian Institution. This change was made for the purpose of dispens- 

 ing with the dead weight of one of the driving bars, and more partic- 

 ularly for introducing the important feature of keeping up the magnet- 

 ism of the driving bar. As soon as this new form was completed and 

 tried, a gain of one half a horse-power was at once realized, and by 

 the addition of a few more feet of battery surface, the power was found 

 to be above four horse. Further addition of battery would still aug- 

 ment the power, and I see no reason why ten horse-power might not 

 be obtained from this engine, by the addition of more battery ; but 

 whether it would be economical to increase power by this means alone, 

 and to ascertain the point, for this and every other engine, beyond 

 which economy would cease by increasing the battery alone, are mat- 

 ters to be determined by experiment. 



" The next important point to be determined was the expense of this 

 power. Much to my own surprise, the expense was found to be less 

 than the most expensive steam-engines, although recently, in Europe, 

 it has been decided by experimenters, and generally conceded, that it 

 was fifty times the cost of the dearest steam-engines ; but this is no 

 obstacle to its introduction, considering its immense advantages in 

 other respects. Moreover, if thus much has been done in the very 

 commencement of the undertaking, what may we reasonably expect 

 from its further prosecution ? Before it can be rendered available in 

 practice, much remains to be done with the galvanic battery, to render 

 its action regular and durable, and in other ways to establish a cer- 

 tainty of action, so that the engines may he managed by persons not 

 thoroughly skilled in the subjects of electricity and magnetism. It 

 remains also to be proved, whether the power will increase in propor- 

 tion to the size of the engines. This principle seems to be strongly 

 indicated by past experiments ; but yet it cannot be established by cal- 

 culation or process of reasoning. Experiment upon an extensive scale 

 can alone determine this point. A part of the work preparatory to 

 the building a locomotive engine has been done ; but it seems ne- 

 cessary to try further experiments before incurring the expense of 

 another large engine upon the plan above mentioned. The rotary form 

 of the engine has not been tested, although it possesses advantages 

 not to be found in any form of the reciprocating engine. There are 

 some obvious disadvantages attending its construction ; but it is hoped 

 that they will be outweighed, more especially as this form of the en- 

 gine will occupy less than one half of the room required for the recip- 

 rocating form. 



" It would seem very desirable that the investigation thus begun, 



