Distribution of Magnetism as affected by Induced Currents, 435 



examined by the author (Mr. Thos. Andrews), the crystalline jointings 

 appearing to be similar in character. 



A general analogy appears also to exist between the crystalline 

 structure of pure platinum and that of pure gold, which is noticeable 

 on comparing the illustrations in the present paper with those in the 

 following papers, viz. : " On the Structure of Gold and Gold Alloys," 

 by Professor J. O. Arnold,* and "On the Structure of Metals, its 

 Origin and Changes," by M. Osmond and Sir Roberts- Austen, t 



This identity of structure is further seen on referring to the illustra- 

 tions in the paper on " The Microscopic Structure of Gold and Gold 

 Alloys," by Mr. Thomas Andrews. J 



DESCRIPTION OF PLATE 6. 

 Micro-crystalline Structure of Platinum. 



Fig. 1. Structure seen in section magnified 50 diameters. Oblique illumination. 

 Fig. 2. Primary and secondary crystals seen in section magnified 120 diameters. 



Vertical illumination. 

 Fig. 3. Primary and secondary crystals seen in section magnified 360 diameters. 



Vertical illumination. 

 Fig. 4. Primary and secondary crystals, magnified 3GO diameters. Vertical 



illumination. 



" The Distribution of Magnetism as Affected by Induced Currents 

 in an Iron Cylinder when Rotated in a Magnetic Field." By 

 ERNEST WILSON, Professor of Electrical Engineering, King's 

 College, London. Communicated by Sir W. H. PREECE, 

 F.RS. Received January 3, Read January 30, 1902. 



One object of this research is to investigate the effect which induced 

 currents have upon the distribution of magnetism in an iron cylinder 

 when it is rotated about its longitudinal axis in a magnetic field 

 whose direction is normally at right angles to the axis of rotation. 

 Another object is to investigate the rate of dissipation of energy by 

 these induced currents, and to compare the same with the result of 

 theory. This second part of the work will be dealt with in a subse- 

 quent paper. 



The variables dealt with are the total flux of magnetism between 



* ' Engineering,' vol. 61, 1896, p. 176. 



t ' Phil. Trans.,' A, 1896, p. 417, fig. 10, Plate 9, and fig. 16, Plate 10. 



J 'Engineering,' September 30, October 28,- December 9, 1898; see also 

 "Micro-metallography of Iron," by Mr. Thomas Andrews, ' Koy. Soc. Proc.,' 

 vol. 58, 1895. 



I wish to acknowledge the grant of 80 for the purposes of this research, 

 which was voted to me by the Council of the Royal Society out of the Government 

 Grant. 



