Page:Proceedings of the Royal Society of London Vol 69.djvu/455

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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 subsequent 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.