128 ANNUAL OF SCIENTIFIC DISCOVERT. 



ON THE MECHANICAL THEORY AND APPLICATION OF THE LAWS 

 OF MAGNETIC INDUCTION AND ELECTRICITY. 



In a paper on the above subject read before the British Association, 

 at its last meeting, by Mr. J. B. Thomson, electricity and magnetism 

 were considered as a force in the same way as heat and light ; and 

 electric and magnetic induction were treated in correspondence with 

 mechanics. The summary of the author's theories is : That the phe- 

 momena 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 co- 

 natus 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 current, or by hardened 

 steel or magnetic iron ore, so that the earth-magnetism may How in ; 

 in act, on its electric projection and recession, or when iron or some 

 other paramagnetic is moved through this sphere. That electric con- 

 dution is by certain molecular movements of particular portions of mat- 

 ter. Those wherein this movement is easily excited ^,re called con- 

 ductors, and those wherein it is with difficulty excited are called insula- 

 tors. That magnetic conduction is by the symmetrical arrangement 

 into a vortical sphere of spirals of a general medium, which pervades 

 all matter, and holds it in that form for the time being. That par- 

 ticular matter wherein the sphere is easily excited is called paramag- 

 netic, and that wherein it is with more difficulty excited is called dia- 

 magnetic. 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 currents of electricity generally, and even by a tan- 

 gent to such spiral. Also it can be induced by magnetic conduction 

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

 on the projection aud recession of this sphere. That this sphere is 

 projected in the direction of the exciting electric current, an 1 recede'.-! 

 in the opposite direction. That the electric force is indued on the 

 projection of the magnetic vortical, and also on its recession. That, 

 consequently, for one inducing current there are two induced cur- 

 rents ; therefore, it would appear that by induction electric excitation 

 is multiplied. Finally, that these inductions and conversions offeree 

 are in strict accordance with the laws of mechanical motion. In con- 

 nection with the paper an induction machine was exhibited, the chief 

 points of novelty in which appear to be these : That it is self-acting ; 

 the current of voltaic electricity which produces the induced current 

 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 

 ten Daniell's cells to that of 1,000, and this without employing more 

 than three or four cells. These are valuable properties to electricians 

 who are engaged in experiments with electricity of high or even mod- 

 erately high tension. Besides, it is applicable'to any batteries what- 

 ever, having been used experimentally for telegraphy and for electro- 

 depositing. For telegraphy through submarine and subterraneous 

 cables there appears to have been a great objection to induction ma- 



