320 APPENDIX. [No. XXIII. 



upon, when there would be neither heat to cheer, light to gladden, sound 

 to enliven, nor motion to excite. 



Nature, however, abhors quiet, and delights in action. In every case 

 where attraction is exerted, it can be destroyed by a new attraction ; and 

 thus, whilst attracted matter exhibits cohesion, composition, and position, 

 so a new attraction can cause disintegration, decomposition, and motion. 

 Hence we deduce the law, " that a new attraction can destroy a former 

 attraction." 



For a study of the effect of a new attraction acting upon attracted 

 matter, the voltaic battery stands forth pre-eminently as an instrument 

 well calculated to exemplify the phenomenon. For a voltaic circuit it is 

 essential to have a fluid compound built up of two atoms only : this com- 

 pound is decomposed by any matter either in a solid, fluid, or gaseous 

 state capable of setting up a powerful attraction between itself and one 

 element of the compound : this is the positive pole. The second element 

 is evolved at the negative pole, and the two points may be connected 

 together by matter extending for miles and miles; a fact on which 

 depend the electric clock and telegraph. In ,a single battery there is but 

 one point at which the new attraction is excited. In the compound bat- 

 tery there are as many points as there are cells in the series. A single 

 voltaic battery may act through a series of similar troughs, provided that 

 in these secondary troughs the tendency to destroy the former attraction 

 is nearly equal to the tendency to maintain it. I place before you an 

 example, in which one battery is reducing gold, silver, copper, tin, lead, 

 iron, zinc, in separate cells, having solutions of the positive poles of those 

 metals. In this case, one grain of zinc in the battery reduces 6t grains of 

 gold, 3i of silver, Si lead, 1 j^ tin, 1 copper, ^^ of a grain iron, these being 

 the relative weight of one atom of each of these metals. 



By the voltaic battery, especially if we employ the platinized silver 

 battery, as is now almost invariably used for heavy work, we obtain results 

 equivalent to the original atti-action within a very trifling percentage, a 

 result which must be regarded as a gloinous triumph of human skill. On 

 account of this perfection of result I have been enabled to construct an 

 instrument which I call a battery-meter, in which every degree shows that 

 a grain of zinc has entered into combination and become sulphate of zinc. 

 By this we can tell the amount and thickness of metal reduced in our 

 precipitating trough. This instrument is the first instance in which man 

 has estimated work done by the primary attraction or source of power. In 

 the steam-engine the coals burnt do not point out so accurately the result 

 obtained ; and I have elsewhere observed that even in the animal, the most 

 perfect of all machines, the food the soldier eats will not of necessity 

 indicate the number of miles traversed, or of the enemy killed. 



This instrument was designed for the Bank of England. Ton are all 

 doubtless aware, that upon my proposition the entire system of printing 

 the Bank of England notes has been changed, and that they are now 

 printed from the surface : a change which has contributed so much to give 

 identity to the note. The original dies are cut in copper, steel, or brass ; 

 from these, moulds are made, which again are electrotyped to make the 

 cast for printing. The battery-meter, placed in the battery, shows us the 

 thickness of our deposited metal in the trough; and though our prac- 

 tised eye enables us to dispense with extraneous aids, I can but think 



