I.S.; 



UNDULATORY FORCES ELECTRICITY. 



[VOLTAIC BATTEKIKS. 



CHAPTER II. 

 VOLTAIC ELECTRICITY 



IT may, perhaps, be no exaggeration to say, that scarcely 

 any branch of experimental science ha* produced to 

 groat a so .K that wliich we are about to 



investigate. Within th<> sli..rt space of some sixty or 

 seventy years, that which was, comparatively speaking, 

 a philosophic toy, lias become the cement of national, 

 social, ami oaatlMNu] relations. The simple oxpcri- 

 nient which, according to the generally received opinion, 

 first gave birth to the idea that electricity could be set 

 free by chemical action, has expanded to an extent far 

 exceeding the most sanguine hopes of its discoverers, 

 and lias become, in its applications, a positive necessity 

 of daily life. 



Most of the remarks ami experiments we have given 

 in connection with frictional electricity, have a decided 

 bearing on the subject with which we now have to deal. 

 Indeed, we shall presume that the student and general 

 reader has entirely mastered all the laws and pheno- 

 mena (so far as the present state of our knowledge will 

 permit) to which reference has already been made. 

 Even the terms and expressions we have employed will 

 have to be constantly repeated in our future pages, and, 

 as such, they will form the groundwork of further 

 progress. 



ry of voltaic electricity, or, as it is some- 

 time* tonne,!, . is connected with tin; early 

 researches of two Italian philosophers. It is state.!, 

 that Calvani first noticed how the contact of a metal 

 with the nerves of the leg of a frog, produced muscular 

 contractions in the limli ; and that Volta, extending the 

 idea, found that the of two metals" was sntli- 

 cient to produce various electric phenomena. \\'e have 

 hitherto can-fully abstained from entering into any dis- 

 cussion as to the relative merits of individual discoverers 

 or inventors. The natural pride and conceit of huma- 

 nity is always prostituting to its own purposes the 



:ties of scientific research which are continually 

 arising ; and we can refer to no fact more degrading to 

 the dignity of human ii , than that its chief 



possessors have, from the days of Newton ami Leibnitz, 

 been found engaging in personal disputes as to the 

 priority of discovery, where humility of mind and a 

 pure love of science ought to have been the reigning 

 principle. Unfortunately, it is too true, that to err is 

 human; and yet wo may, and ought not to be too 

 in in our hopes, if we predict that the. day will 

 arrive when the con - of having extended the 



limits of our knowledge, and of having been the in- 

 struii i ig our fellow-creatures, shall be the 



! reward to which "philo ; i aim at. 



ii useless for us to describe the contests which took 

 place, many years ago, between those who maint: 

 the ii contact, and others who advocated the 



idea of chemical action, as the cause of the development 

 of voltaic electricity. The former imagined that the 

 mere contact of two dissimilar metals was the sole ex- 

 citing cause. Dr. Faraday, however, by a series of 

 masterly researches, proved, that on such contact taking 

 place, chemical action instantly ensued ; and, further, 

 that electricity was evolved by chemical action in cir- 

 cumstances where contact was impossible. We may add, 

 that just in proportion to the chemical action in a 

 voltaic battery, so the quantity of electricity set free is 

 increase,! ; aiid, at the present time, we are not aware 

 that any advocates of the contact theory are to be found. 

 We shall at once proceed with our subject, and com- 

 mence our experiments with voltaic batteries. 



VOLTAIC BATTERIES. 

 IT is ail unfortunate circumstance, that many of the 



Fig. 37. 



terms employed in science do not sufficiently indicate 



tin- moaning and object they are intended to express; 

 and hence the beginner incessantly finds obstacles to 

 his progress. An amusing illustration of the ignorance 

 of even well-educated persons, with respect to this point, 

 came under our notice whilst effecting a fire insurance 

 some years ago. The agent of an office gravely ohji cud 

 to tli the premises ; 



expressing an opinion that tin hly dangerous, 



and enforcing his views by Mating that they never 

 issued a policy when ; /iui/... ><-./,, was kept in a building. 

 He had confounded the term lmtt< nj with its military 

 signification, and was utterly surprised to see fifty cells 

 of Grove's "batteries," ' ,uth acid and water, 



instead of the matfritl of warfare. 



A voltaic battery is a combination of cells, each con- 

 taining the materials requisite to the production of 

 electricity by chemical action ; and we shall now pro- 

 ceed to examine such arrangements theoretically and 

 practically. 



If a piece of zinc and a silver coin 1 on 



either side of the tongue, no sensation of any sort is 

 experienced until they come in contact in some part : 

 but on that taking place, a peculiar metallic taste is 

 ived in the mouth. The elements of a voltaic 

 battery arc employed in this e\, A current of 



electricity is excited by the action of the moisture of 

 the tongue on the 

 zinc ; and it passes 

 from the zinc, 

 through the liquid 

 to the silver, at 

 theirpoint of junc- 

 tion, and BO back 

 to the zinc again. 



A more satisfac- 

 tory mode of il- 

 lustrating this in- 

 ii.g fact, is 

 ated in the 

 annexed engrav- 

 ing- 



rvmtnt 32. 



Place a sheet of zinc which has been cleaned in a 

 little sulphuric acid and water, and rubbed over with 

 mercury till it is quite bright, in a glass vessel, and 

 opposite to it a sheet of copper, so that they do not 

 touch. The glass is then to be nearly tilled with a 

 mixture of one part of sulphuric acid to eight parts 

 of water. No action of any sort will he perceived. 

 But if a wire be placed aci . s re- 



nted in I that it may join the two, 



a current of electricity will pass from the zinc 

 plate, 2, through the liquid to the copper plate, c, 

 and, passing by the wire, >, in the direction indicated by 

 the arrow, it will at last return to the zinc plhte ; 

 abundance of hydrogen will be given off from the 

 copperplate. If the wire be broken in any part, and 

 its extremities bo kept in contact with each plat*;, the 

 tongue will feel the same sensation when in contact 

 with the ends of the wire, as that which we have 

 already alluded to ; and thus the existence and passage 

 of an electric current will bo at once made evident to 

 the senses. Each of the plates of the battery is 

 named in accordance with the theories we have already 

 discussed in the last chapter. * The zinc plate is called 

 the positive, and the copper the negative, element of 

 the battery; and we may here lay down, as a general 

 rule, that that metal wliich is most acted uuon in a 

 voltaic batterv, is positive to the other metaL 



Sec ante, p. 17ft. 



