44 Dr. E. Taylor Jones. 



Found. Calculated. 



Si0 2 33-33 33-35 



BaO 48-48 48-20 



ALA 6-06 6-02 



B 2 3 12-12 12-40 



99-99 99-97 



Specimen XXIV. 



The "Jena" glass is essentially a borosilicate of zinc, soda, and 

 magnesia, containing 



20SiOa,2ZnO,2MgO,3NmO,2B a O a . 



Found. Calculated. 



Si0 2 67-87 68-05 



ZnO 9-03 9-11 



Na 2 10-04 10-46 



MgO 5-02 4-50 



B 2 3 8-03 7-87 



99-99 99-99 



"On the Magnetic Deformation of Nickel." By E. TAYLOR 

 JONES, D.Sc. Communicated by Professor ANDREW GRAY, 

 F.R.S. Received February 8, Read February 17, 1898. 



On a former occasion a paper was communicated to the Royal 

 Society* containing an account of some measurements of the mag- 

 netic contraction of a nickel wire, and a comparison of these with 

 the values deduced from Kirchhoff s theory. It was there shown 

 that the most important term in the calculated value of the elonga- 

 tion of a long wire of soft magnetic metal is represented by 

 JH(I/<5P), where H is the magnetising field and 1 the increase of 

 magnetisation produced by a small increase of longitudinal tension 

 P per unit area. The results showed that the observed contraction 

 in nickel was much greater than the calculated value. It was then 

 sought to establish an empirical equation which might represent the 

 observed effects, and it was found that the difference between the 

 observed and calculated contraction was approximately proportional 

 to the fourth power of the magnetisation. 



It was suggested to me at the time that this result should be 

 tested by repeating the experiments under different conditions in 

 order to find out whether it was generally true. 



* ' Phil. Trans./ A, vol. 189 (1897), p. 189. 



