TRANSACTIONS OF THE SECTIONS. 29 



The author proceeded to say that the foundation of all exact science is number, 

 weight, and measure ; and that, as observed by an eminent writer, no branch of phy- 

 sical knowledge could be held as being out of its infancy which did not in some way 

 or the other frame its theory, or correct its practice with reference to these elements. 

 He here described and explained the nature of a series of very beautiful instruments, 

 by which the quantity of the electrical agency, its attractive force, its explosive 

 power, and the effects produced, could be accurately measured. Having thus en- 

 deavoured to bring the unknown agency we term electricity under the dominion of 

 number, weight, and measure, the leading characteristics of electricity as a force 

 were next brought under consideration. And first, we observe electrical power 

 exhibits itself under two forms, usually termed vitreous and resinous electricity, or 

 positive and negative electricity. These have been usually considered as arising 

 out of two distinct and separate fluids, or of a single elementary fluid in a greater or 

 less state of condensation. They are, however, one and the same force, and have 

 the same relation to each other as the forces of compression and extension in the 

 case of a bent bow or spring. We cannot have one without the other ; and as in 

 the latter instance we should gain but little by assuming the existence of elastic 

 fluid or fluids as the source of elasticity, so in the case of electrical force we may as 

 well look at once upon positive and negative electricity as elementary facts of which 

 we have no adequate explanation. 



Secondly, we observe that whatever be the nature of electricity as a physical 

 agency, it cannot exert itself equally in all directions at the same moment. In the 

 case of gravity, the sun does not attract the earth with less force because it is 

 exerting its gravitating power on the other planets. Such is not the case in the 

 development of electrical force. The author here introduced a striking experiment 

 in illustration of this ; showing that a delicate electroscope, attracted toward an 

 electrified circular plate placed vertically, became less forcibly drawn toward the 

 plate from a distance when a second body was brought to share in the action. This 

 is the result of a third characteristic of electrical force, termed electrical induction 

 or influence, the laws and operation of which were now further explained and illus- 

 trated. It is solely upon this species of electrical action, apparently of a sympa- 

 thetic kind, operating at a distance, probably by propagation through the intervening 

 medium, that electrical attractive force altogether depends: without it no exertion 

 of power is possible. In electrical force bodies are first rendered attractable before 

 they become attracted, and for the regular and full exertion of the attraction, both 

 the bodies must be susceptible of unlimited electrical change. When this is the case 

 the development of force is easily traced ; and the force will be found to vary as the 

 square of the quantity of electricity in operation directly, and as the squares of the 

 distances inversely : of this some striking and very interesting experimental illustra- 

 tions were given through the instrumentality of the electrical balance, delicately set 

 up with complete means of adjustment for distance and force; and it was with re- 

 markable precision the beam descended when under the influence of two attracting 

 surfaces ; the quantity of electricity and the weights being given, the force of in- 

 duction, upon which the resulting force depends, varies in the simple inverse ratio of 

 the distance between the attracting surfaces, and depends, first, upon the direct in- 

 fluence of the electrified surfaces, secondly, upon a reflected induction thrown back 

 upon the excited body. The total force is in a compound ratio of these forces, and 

 it is in this way we obtain a force in the inverse duplicate ratio of the distances. If 

 from any cause either or both of the previous elementary actions be interfered with, 

 then we have no longer this law ; so that any law of electrical force is possible, as 

 found in the experiments of many eminent philosophers of past days — Muschenbroek, 

 Brook, Taylor, Whiston, Martin, and others. The author thinks that the results of 

 the experiments of these eminent men have been called unjustly in question ; every 

 result they arrived at is producible by careful manipulation. 



The author now brought under consideration the question of electrical force be- 

 tween spheres, one charged with electricity, the other neutral and in a free state. 

 This question had been often elaborately treated, and had been hitherto considered 

 a physico-mathematical question of great intricacy. An analysis of the elements of 

 this question was here entered upon. Upon the proved facts that the force varies 

 with the quantity of electricity and is in the duplicate inverse ratio of the distance, 



