MODERN VIEWS AND PROBLEMS OF PHYSICS. 517 



of research, and the degree of precision attainable. The trust- 

 worthiness of the method is shown by the close agreement be- 

 tween its results when applied to the other planets, and the veloci- 

 ties computed from the known astronomical motions of the same 

 bodies. 



It is usually thought necessary to caution students of elec- 

 tricity against regarding either of the hypotheses, known respect- 

 ively as the two-fluid and the one-fluid hypothesis, in the light of 

 an assured thing, and the lecturer commonly hastens to declare 

 that no one knows what electricity is. The declaration is as just 

 as the caution ; but it is not in human nature to allow such a 

 declaration long to stand unchallenged. The very fact that it is 

 possibly correct is a stimulus to investigation. Recent research 

 has not conclusively shown what electricity is, but it has consid- 

 erably shaken the foundations of the above assertion regarding it, 

 and some singular views have been developed that indicate light 

 ahead. We are learning that although the terms " electrification " 

 and " electric " may continue in service to express a condition of 

 matter or to characterize particular phenomena, yet the very name 

 " electricity " may probably become useless and vanish from the 

 vocabulary of physics, for the reason that, instead of electricity 

 being any object, it is probably only a mode in which the ether 

 makes itself manifest. One of the latest views, strongly advo- 

 cated, is that ether may be analyzed into two constituents, equal 

 and opposite, each endowed with inertia and each connected with 

 the other by elastic ties which are weakened or dissolved by the 

 presence of gross matter. The two constituents are called posi- 

 tive and negative electricity respectively, and of these two elec- 

 tricities the ether is composed. Electric currents which are ob- 

 tained in such diversity and magnitude for commercial purposes 

 are in almost every case the result of electro-magnetic induction, 

 and are not due to the action of a battery. Yet there is no differ- 

 ence electrically between the currents obtained in the two ways. 

 Maxwell's theory, which treats electro-magnetic action as a varia- 

 tion of ether stress in the medium in which the conductor is situ- 

 ated, may be applied to the conductors of battery currents also, and 

 the medium surrounding the conductor in all cases is the home of 

 the energy transmitted (as we are in the habit of saying) along the 

 wire. But the energy is not transmitted by the wire; on the con- 

 trary, the wire, in just so far as it is a good conductor, fails to 

 transmit the energy (the strain) which the action of the generator 

 has sent out into the surrounding medium, and which breaks 

 down or gives way in the conductor. " The energy of a dynamo 

 does not, therefore, travel to a distant motor through the wires, 

 but through the air. The energy of an Atlantic cable does not 

 travel through the wire strands, but through the insulating 



