1888.] Electro-chemical Effects on Magnetising Iron. 153 



introduce numerous modifications of detail and also some entirely new 

 modes of experimentation hereafter referred to. Fig. 3 shows the 

 form of apparatus, coil of 750 wraps, &c, used with the larger iron 

 and steel bars. In this apparatus the ends of each pair of bars were 

 deeply immersed in the solution contained in the vessel D, below the 

 coil ; liability to possible temperature errors from any heating of the 

 coil was thus obviated. The unmagnetised bar B was made shorter 

 than the bar A in the coil, so as to avoid partial magnetisation from 

 outside induction of the coil, which would have been more liable to 

 occur had the bar stood in full length parallel with the coil. This 

 arrangement was found preferable when using large steel bars, as 

 induced magnetism to any considerable extent of the bar B would 

 have detracted from the full effect. In some instances, however, this 

 precaution was not adopted. The apparatus, coil, &c, used with the 

 smaller iron and steel bars is shown in fig. 4. A single-cell bichro- 

 mate battery was employed in connexion with the coil for magnetisa- 

 tion during all the experiments recorded in this memoir. 



Fig. 3. Fig. 4. 



Scale 2 inches = 1 foot. 



The bars were of specially prepared wrought iron and cast steei ; 

 the smaller bars were 8 J inches long, 0261 inch diameter, and the 

 larger bars were f -inch diameter, the longer one (A) was 10J inches 

 long, and the shorter one (B) 5£ inches long ; all the rods were finely 

 polished. The general physical properties of the metals are given in 



