ELECTRICITY AS A MOTIVE POWER. 351 



its first discovery J}y Oersted, in 1819, and first application to 

 actual rotary motion by Faraday. After explaining and illus- 

 trating by many novel experiments the character and direction 

 of the force exercised by voltaic currents upon magnets, Mr. 

 Grove pointed out thr.ee definite ramifications of the force which 

 different experimentalists had sought to apply to the practical 

 production of mechanical motion : I. The immediate tangen- 

 tial or deflective power of the current, which is shown in the 

 ordinary galvanometer, where a magnet is deflected by a 

 stationary wire affected by a voltaic current, and in the re- 

 volving wheel of Barlow, where the radii are deflected and 

 revolve by the influence of a stationary magnet. 2. What is 

 called the suspension principle, where powerful stationary 

 electro-magnets are made to attract pieces of soft iron placed 

 in the periphery of a wheel. As each piece arrives opposite 

 the magnet, the voltaic current is interrupted by the revolution 

 of the wheel itself, and this passes on until the next piece 

 comes within the influence of the magnet, which, being re- 

 electrised, again attracts, and so on in rotation. 3. The prin- 

 ciple of inversion of polarity, first introduced by Dr. Ritchie. 

 In this two sets of magnets are employed, the one set 

 stationary, and the other rotary ; the poles of the last being 

 alternately changed by inversion of the voltaic current, the 

 attractions of the two opposite poles of powerful magnets are 

 rendered available. 



Beautiful working models of the application of the several 

 principles were exhibited, most of them representing patented 

 machinery. 



Mr. Grove then entered upon the statistics of expense of 

 electro-magnetic machines. It appears from the experiments 

 of Dr. Botto, of Turin, that the consumption of 45 Ibs. of zinc 

 is necessary to work a one-horse power magnetic machine for 

 twenty-four hours. Dr. Botto worked with Mr. Grove's bat- 

 tery, against which, although admitted to be by far the most 

 powerful and equal in constancy to any other form, a general 

 notion prevails that it is expensive. This Mr. Grove says is 

 not the case, and gave his reasons, as follows : To contrast 

 the current cost of the nitric acid or Grove's battery with the 

 apparently cheapest form namely, a battery charged with 



