148 Analyses of Boohs. [Feb. 



6. Two opinions have been broached to explain the effect of elec- 

 tricity by friction, viz : that it is derived from the adaptation of the 

 asperities of the surfaces rubbed upen each other, or from the reci- 

 procal action of the atoms of bodies upon each other. In favour of 

 the first opinion it is argued that the electrical excitement is great 

 in proportion to the roughness of the bodies subjected to friction j and 

 in support of the second the fact is brought forward, that if two 

 plates of glass or marble are slid upon each other so as perfectly to 

 cover each other's surfaces, they adhere powerfully to each other 

 independently of atmospheric pressure, for the same result occurs in 

 a vacuum. The author has performed a number of experiments for 

 the purpose of settling this question, from which it appears that the 

 disengagement of electricity seems to depend on the state of the divi- 

 sion of the parts of bodies and of the rapidity of friction, and that the 

 body whose parts undergo the most displacement has a tendency to 

 produce negative electricty. 



The causes which determine the disengagement of electricity in 

 non- conductors are difficult of appreciation, but the state of their 

 surfaces has a greater influence upon the nature of the electricity, 

 than in the metals. Delarive conceived that all the metals when 

 they are rubbed with wood, the hand, or cork, &c, become nega- 

 tively electrical. Haiiy has given the name Disthene to a crystal- 

 lized mineral, whose surfaces have such an influence upon the nature 

 of the electricity disengaged in the friction of bad conductors, that 

 positive electricity is exhibited on certain faces, and negative on 

 others, by the same friction, without any apparent distinction be- 

 tween them. 



Friction in a great number of cases may give origin to chemical 

 re-action, and electrical effects of chemical origin, have been some- 

 times attributed to purely physical causes. Becquerel is inclined to 

 conclude, however, that although chemical action is the most influen- 

 tial agent in the production of electricity, yet, that in the present 

 state of the science, it is not proper to abandon the theory of Volta, 

 in regard to developement by contact. Faraday considers contact to 

 have no influence. 



7» Ampere was the first person who endeavoured to produce 

 electrical currents by the influence of other currents, but he merely 

 broached the fact, while Faraday following it out, has formed on it 

 an important branch of electricity. To the power which electrical 

 currents possess of exciting electricity, he has applied the term 

 induction, the induced current, occasioned by the action of the in- 

 ducing current being directed in a contrary direction. He has fully 

 confirmed the idea of Ampere, that magnets may be considered as 

 formed of electrical currents, turning round their molocules in a 

 direction perpendicular to their axis. 



The author, after considering the sources of electricity of which 

 we have given an outline, proceeds to lay down the laws which 

 regulate its action. 



He explains the important law demonstrated by Coulomb, that the 

 particles of electricity repel each other inversely as the square of the 

 distance. Coulomb has shewn that the loss of electricity .in the 



