1884.] 



On Magnetic Polar 



rity and Neutrality. 



405 



Rodwell, George F., F.R.A.S. T 



Roy, Prof. Charles Smart, M.D. T 



Riicker, Professor Arthur Wil- T 



Ham, M.A. T 



Smith, Willoughby. T 

 Spiller, John, F.C.S.. 



Stotherd, Richard Hugh, Colonel "V 



R.E. 



Tate, Professor Ralph, F.G.S. V 



Tenison- Woods, Rev. Julian E., Y 

 M.A. 



The following Papers were read : — 



Thomson, Joseph John, M.A. 

 Tidy, Charles Meymott, M.B. 

 Tonge, Morris, M.D. 

 Topley, William, F.G.S. 

 Tribe, Alfred, F.C.S. 

 Vivian, Sir H. Hussey, Bart. 

 Warren, Sir Charles, C.M.G., 



Lieutenant-Colonel R.E. 

 Warrington, Robert, F.C.S. 

 Watson, Professor Morrison, 

 M.D. 



I. "Magnetic Polarity and Neutrality." By Professor D. E. 

 Hughes, F.R.S. Received February 23, 1884. 



In recent papers upon the Theory of Magnetism,* I gave the 

 opinion drawn from a long series of personal researches, that mag- 

 netism in iron and steel is entirely due to the inherent polarity of its 

 molecules, the force of which could neither be destroyed nor aug- 

 mented ; that, when we have evident magnetism, the molecules rotate 

 -so as to have all their similar polarities in one direction ; and that 

 neutrality is a symmetrical arrangement or a balancing of polar 

 forces, as in a closed circuit of mutual attractions. The series of 

 researches which I now present bear unmistakable testimony to the 

 truth of these views, showing the opposite polarities which exist in 

 &n apparently neutral bar of iron ; and that it is by this means alone 

 that external neutrality occurs in the iron cores of an electro-magnet 

 upon the cessation of the inducing current. 



The instrument used for measurementsf consists of a delicate silk 

 fibre- suspended magnetic needle, always brought to its zero-mark by 

 tthe influence of a large magnet at a distance, the angle of which 

 gives the degree of force required to balance any magnetised body 

 placed on the opposite side of the needle. It can also employ electro- 

 magnetic effects by the use of two opposing coils on each side of the 

 needle, balanced so that an electric current passing through the coils 

 has no influence on the needle, except when a piece of iron or steel is 

 placed inside one of the coils ; this again being balanced and 

 measured by the large revolving magnet. 



* "Proc. Eoy. Soc." (vol. 35, p. 178), and "Journal of the Society of Tele- 

 graph Engineers," vol. xii, 1883. 



f " On a Magnetic Balance, and Eesearches made therewith," by Professor D. E. 

 Hughes, " Proc. Eoy. See." (vol. 36, p. 167). 



2 f 2 



