SECTION III. 



ELECTRICITY, AND ITS APPLICATIONS. 



CHAPTER I. 

 FRICTIONAL ELECTRICITY. 



HAVING already considered separately the forces of 

 Heat and Light, we shall now undertake the investi- 

 gation of phenomena connected with that of Electricity. 



As a branch of experimental science, electricity is 

 of comparatively modern date. It is true that the 

 ancients were acquainted with what we should now 

 term elementary facts. Thus, Thales was aware that 

 certain resinous substances, especially amber, would, on 

 being sharply rubbed, attract fight bodies to its surface. 

 It was not, however, till within the last century, that 

 such, and similar results, were philosophically inves- 

 tigated, and the foundation of electrical science was 

 i'1'ly laid. 



We shall not expend any space in a separate historical 

 iketch of our subject ; such will naturally fall into our 

 pages as we describe various apparatus which have been 

 invented with the object of illustrating the electrical 

 phenomena. The unpleasant office will thus be avoided, 

 of deciding the relative claims which have been advanced 

 on the part of individuals, as to their just rights to the 

 merits of discoveries they have made ; which are at all 

 times liable to be unsatisfactorily dealt with, and to call 

 up the criticisms of a host of partisans. 



The term ' ' electricity" has been derived from the Greek 

 word "electron," which signifies amber; and as such, 

 the science and its name are associated with the early 

 experiments of Thales, the Milesian philosopher. 



We have endeavoured to familiarise the minds of our 

 readers with the doctrines of latent forces in our two 

 previous sections.* Electricity, like light and heat, is 

 obedient to the same law ; and, so far as our experience 

 goes, there is no body with which we are acquainted, 

 which cannot afford us, if proper means are employed, 

 some evidence of the existence of electricity. 



There are, however, chiefly two sources which we can 

 employ for the purpose of disturbing the electrical equi- 

 librium ; or, in other words, of educing electric forces : 

 these are motion, or mechanical action, which is chiefly 

 employed under the form of friction ; and chemical 

 action, when it takes place in the union or division 

 of two or more bodies. There is, however, another 

 ource namely, that of magnetism, which, by a pecu- 

 liar arrangement, affords us what has been frequently 

 termed the electric fluid. 



It U proper that we should here explain some terms 

 which are continually employed by writers on electri- 

 city. These are, "current," "fluid," itc. ; and which 

 had their origin in the speculations of early experimen- 

 ters. Even in the jmrlniux of daily life these terms are 

 often employed ; and thus it is frequently stated, " that 

 the electric fluid" struck a building. 



These terms, and expressions involving them, have 

 great convenience in conveying the idea of a passing 

 or moving force. Hence, strictly philosophical defini- 

 tions often contain such remarks as, that "the electric 

 current" pinups in a certain direction. Now, our 

 modern views classify electricity with the undulatory 

 forces ; and we equally believe in the idea of electric, as 

 * Sec unit, pp. 13 and 41. 



VOL I. 



in that of calorific and luminous undulations. If, there- 

 fore, in the following pages, we employ the terms to 

 which we have referred, our readers must understand 

 that we do so with the limitations we have mentioned, 

 and that we simply consult the convenience of expres- 

 sion rather than peculiar exactness of speech. 



Having thus guarded our future progress against any 

 charge of looseness of expression, we shall now proceed 

 to examine generally the various means by which the 

 electric force is excited, the machines which are em- 

 ployed to illustrate its effects, and the laws which have 

 been found as governing the occurrence of electrical 

 effects. In doing this, we shall afford a vast variety of 

 experiments, each of which may be readily tried by the 

 student ; and shall also put him in possession of means 

 by which he may pursue his investigations at a compara- 

 tively moderate cost. We must defer the consideration 

 of electricity, as produced by magnetic action, to a 

 separate section, and confine our attention in this to 

 the subjects of 



1. Frictional Electricity. 



2. Voltaic Electricity. 



FRICTION At ELECTRICITY. When the particles of any 

 body are disturbed from their quiet, and put in motion, 

 there always results the production of heat, light, or 

 electricity. They seem associated with matter in all its 

 varied forms ; and thus we find them in every state or 

 condition of all bodies surrounding us. 



The most ready means of evolving these forces is that 

 of friction, of which daily life affords us numerous 

 instances. The simple experiment of striking a lucifer- 

 match will produce heat and light ; and by means of a 

 piece of apparatus, which we shall describe as we pro- 

 eeed, the evolution of electricity is also detected. 



Former writers on electricity divided bodies into two 

 classes namely, electrics, and non-electrics. In the 

 former, glass, resins, fur, silk, itc., were included ; 

 whilst the metals, because they did not seem to evolve 

 electricity by friction, were termed non-electrics. At 

 the present time, however, metals are the chief sources 

 whence we obtain the force, the rationale of which we 

 shall explain under the head of Voltaic Electricity. 



The following experiments will illustrate the produc- 

 tion of electricity by friction, and also exhibit some of 

 the phenomena which attend its presence in a free state. 



Esperitnent 1. Dry a glass tube about eighteen inches 

 long and an inch in diameter, by means of a cloth, 

 warming it occasionally before a fire. Having also 

 dried an old silk handkerchief, rub it briskly on the 

 tube, and then hold the latter near to some feathers or 

 small pieces of paper. These will be attracted to the 

 tube, on which they will adhere for some time ; they 

 will, however, fly from it, returning to the table, again 

 to fly to the tube. This motion they will continue until 

 the electrical state of the tube is restored to the same 

 condition as that of surrounding bodies, when the effect 

 will cease. 



Esperiment 2. Repeat the same experiment, but em- 

 ploy a roll of sealing-wax or of sulphur, a piece of 



