TRANSACTIONS OF THE SECTIONS. ]5 



iron of the ship, while the card is brought to a convenient position to he seen by 

 the pilot ; and suspending- the moyeable poi-tion in a liquid, so as to ensure entire 

 freedom from friction, that the needle may obey the polar force, at the same time 

 that great steadiness is secured for the card. 



On the Mechanical TJieory and Application of the Laivs of Magnetic 

 Induction and Electricity. Bij J. B. Thompson. 

 In this paper electricity and magnetism were considered as a force in the same 

 way as heat and light ; and electi'ic and magnetic induction were treated in corre- 

 spondence with mechanics. The summaiy of the author's theories is : — That the 

 phenomena called electricity and magnetism are two forms of force which may 

 either be in conatus or in act. If in conatus, they are in a state of tension ; if in 

 act, then in a state of fluxion. Electricity is in conatus when in the static form of 

 excitation, or when the voltaic circuit is not completed ; in act, when the matter 

 highly excited is brought in contact with matter less highly excited, or when the 

 voltaic circuit is completed. Magnetism is in conatus when the magnetic vortical 

 sphere is held constant by a constant electric cmTent, or by hardened steel or mag- 

 netic iron ore, so that the earth-magnetism may flow in ; in act, on its electric projec- 

 tion and recession, or when iron or some other paramagnetic is moved through this 

 sphere. That electric conduction is by certain molecular movements of particidar por- 

 tions of matter. Those wherein this movement is easily excited are called conductors, 

 and those wherein it is with difficulty excited are called insulators. That magnetic 

 conduction is by the symmetrical an-angement into a vortical sphere of spirals of a 

 general medium, which pervades all matter, and holds it in that foiin for the time 

 being. That particular matter wherein the sphere is easily excited is called para- 

 magnetic, and that wherein it is with more difficidty excited is called diamagnetic. 

 That this sphere can be fixed by means of hardened steel or magnetic iron ore. That 

 the magnetic vortical can be excited by means of spiral cuiTcnts of electricity 

 generally, and even by a tangent to such spiral. Also it can be induced by mag- 

 netic conduction in paramagnetics. That the magnetic force is only in a state of 

 fluxion on the projection and recession of this sphere. That this sphere is pro- 

 jected in the direction of the exciting electi-ic cun-ent, and recedes in the opposite 

 direction. That the electric force is induced on the projection of the magnetic vor- 

 tical, and also on its recession. That, consequently, for one inducing current there 

 are two induced currents ; therefore, it would appear that by induction electric ex- 

 citation is multiplied. Finally, that these inductions and conversions of force are 

 in strict accordance with the laws of mechanical motion. In connexion with the 

 paper an induction machine was exhibited, the chief points of novelty in which ap- 

 pear to be these : — that it is self-acting ; the current of voltaic electricity which 

 produces the induced cmTent also drives the machine ; that the machine can be so 

 adjusted that the quantity and intensity of the induced current shall range from 

 that of 10 DanieU's cells to that of 1000, and this without emplojing more than 

 three or four cells. These are valuable properties to electricians who are engaged 

 in experiments with electricity of high or even moderately high tension. Besides, 

 it is applicable to whatever batteries are, liavmg been used experimentally for tele- 

 graphy and for electro-depositing. For telegi-aphy through submarine and subter- 

 raneous cables there appears to have been a great objection to induction machines, 

 or rather induction coils. The objection was, that these induction coils sent their 

 electricity through the cables in sudden intense shocks, which injured the insulation 

 of the cable. In this machine it is apparently a continuous flow, and no spark vdW 

 jump from one electi'odeto the other, unless first brought in contact, as in batteries. 

 "VMien modified for electroplating it is much more efficient than the ordinarj^ bat- 

 tery ; for though it deposits the metal more slowh' on any one article, yet it de- 

 posits it much more firmly and with a better surface than the ordinarj' battery does ; 

 and it will deposit the same quantity on a thousand articles at once, which enables 

 it to deposit ten times more metal in the same time than its own exciting battery 

 would ao. The construction of the machine is simple, and ■will not be easily de- 

 ranged or speedily worn out. 



