120 Mr. T. Andrews. [Jan. 22, 



January 22, 1891. 

 THE ASTRONOMER ROYAL, V.P.R.S., in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



The following Papers were read : 



I. " On the Unsymmetrical Distribution of Terrestrial Mag- 

 netism." By HENRY WILDE, F.R.S. Received Novem- 

 ber 20, 1890. 



[Publication deferred.] 



II. "The Passive State of Iron and Steel. Part II." By 

 THOS. ANDREWS, F.R.SS.L. and E., M.Inst.C.E. Received 

 October 24, 1890. 



In Part I of this research ('Roy. Soc. Proc,,' vol. 48, p. 116), the 

 author showed the influence of magnetisation on the passive state of 

 iron and steel, and he has now the pleasure of communicating to the 

 Royal Society the results of a further study of certain temperature 

 and other conditions affecting the passivity of these metals in con- 

 centrated nitric acid. The experiments of Series III, in this paper, 

 relate to the effect of temperature, and the observations of Series IV 

 refer to the influence exerted by nitric acids, of varied concentration, 

 on the passive condition of iron and steel. 



SERIES III. 

 Effect of Temperature on the Passivity of Iron and Steel. 



The bars selected for these observations were unmagnetised polished 

 rods, which had been previously drawn cold through a wortle ; a pair 

 of bars of each metal were cut adjacently from one longer bar, and 

 then placed securely in the wooden stand, W ; each bar was 8 j- inches 

 long, 0'261 diameter. The JJ-tube containing 1^ fluid oz. of nitric 

 acid, sp. gr. 1'42, was rigidly placed in an arrangement as shown on 

 fig. 3. One limb, A, was surrounded by a tank containing water, the 

 other limb, B, by a tank of the same capacity, containing powdered ice; 

 the arrangement was such that the water-tank could be heated by a 



