Mr. H. Tomlinson on the Physical Properties of Iron. 245 



amount. Removal from the helix and shaking in a zero 

 field sufficed to restore the wire to its initial condition. 



Similar experiments upon an annealed wire of " best spring 

 steel ,? showed no sensible change of effect when the steady 

 force was varied from to about 16 C.Gr.S. In this case the 

 ratio of length to diameter was about 300. 



We may now regard it as established : — 



That in any condition of force and magnetization, the sus- 

 ceptibility to small periodic changes of force is a definite, and 

 not very small, quantity, independent of the magnitude of the 

 small change. 



That the value of the susceptibility to small changes of force 

 is approximately independent of the initial condition as regards 

 force and magnetization, until the region of saturation is ap~ 

 proached. 



Telling Place, Witham, Essex, 

 Jan. 24, 1887. 



XXVI. The Permanent and Temporary Effects on some of the 

 Physical Properties of Iron, produced by raising the Tempe- 

 rature to 100° C. By Herbert Tomlinson, B.A. * 



Introduction. 



EOE- many years I have been carrying on researches re- 

 specting the effects of stress on the physical properties of 

 matter, and during this period I have become acquainted with 

 certain phenomena, which, though pertaining more or less to 

 most metals, are so conspicuous in iron as to render it worthy 

 of special attention. As these phenomena bear importantly on 

 what Sir William Thomson has designated the thermodynamic 

 qualities of metals, the investigation of which seems to be 

 attracting daily more and more attention, I propose to lay 

 before the Physical Society, from time to time, such informa- 

 tion concerning them as a patient study has enabled me to 

 acquire. 



On the present occasion I would invite attention to certain 

 remarkable effects produced on some of the physical proper- 

 ties of iron, by merely raising the temperature to a degree 

 not exceeding 100° C. 



The Internal Friction of Iron. 



If an iron wire be suspended vertically with its upper extre- 

 mity clamped to a rigid support, and its lower one clamped or 

 soldered to the centre of a horizontal bar of metal, attached 



* Communicated by the Physical Society : read January 22, 1887. 



