406 Mr. S. Bid well. On the Changes produced by [Mar. 1, 



Seebohm, Henry, F.L.S. 



Sharp, David, M.B. 



Shaw, Professor Henry Selby 

 Hele, M.I.C.E. 



Sollas, Professor William John- 

 son, D Sc. 



Stevenson, Thomas, M.D. 



Stewart, Major-Gren. J. H. M. 

 Shaw, R.E. 



Stokes, Sir William, M.D. 



Teale, Thomas Pridgin, F.R.C.S. 



Tenison- Woods, Rev. Julian E., 

 M.A. 



Thomson, Professor John Millar, 

 F.R.S.E. 



Thorne, Richard Thorne, M.B. 

 Tidy, Professor Charles Meymott, 

 M.B. 



Tizard, Thomas Henry, Staff- 

 Commander. 



Todd, Charles, M.A. 



Tomlinson, Herbert, B.A. 



Topley, William, F.G.S. 



Trimen, Henry, M.B. 



Ulrich, Professor George Henry 

 Frederic, F.G.S. 



Ward, Professor Henry Marshall, 

 M.A. 



White, William Henry, M.I.C.E. 



The following Papers were read : — 



I. " On the Changes produced by Magnetisation in the Dimen- 

 sions of Rings and Rods of Iron and of some other Metals." 

 By Shelford Bidwell, M.A., F.R.S. Received February 9, 

 1888. 



(Abstract.) 



In a paper commnnicated to the Royal Society in 1885,* the author 

 has shown that the elongation which an iron rod undergoes when 

 magnetised does not, as had been generally believed, remain unchanged 

 at a maximum when the magnetising force exceeds that which is suffi- 

 cient to produce so-called saturation. On the contrary, he finds that 

 when the magnetising force is continually increased beyond this limit, 

 the elongation becomes gradually less and less, until the rod, after first 

 returning to its original length, ultimately becomes actually shorter 

 than when in the unmagnetised condition. 



The experiments described in that paper are, however, open to 

 objection, on the following grounds : — (1) The field due to the mag- 

 netising solenoid was not quite uniform ; (2) the effect of the ends of 

 the rods was uncertain, and might have played some material part 

 in the production of the phenomena in question ; (3) all the rods used 

 in the experiments retained a certain amount of permanent magne- 

 tism ; (4) the experiments might with advantage have been carried 

 further. The paper now offered to the Society contains an account of 

 some new experiments which were designed to meet the above objec- 

 tions. 



Objections (1) and (2) were met by using rings instead of rods of 

 * ' Koy. Soc. Proc.,' vol. 40, 1886 (No. 242, p. 109). 



