( 527 ) 



XIII. — The Strains produced in Iron, Steel, and Nickel Tubes in the Magnetic 

 Field. Part I By Professor C. G. Knott, D.Sc, F.R.S.E. (Plates L-VI.) 



(Read 6th January 1896.) 

 CONTENTS. 



PAGE 



§ 1. Introduction, . 527 



§ 2. The Tubes, . . . . . . .528 



§ 3. Fixing of Capillary to Tube, . . . .528 



§ 4. The Temperature Effect, . . . . .530 



§ 5. Dimensions of the Tubes, 530 



§ 6. The Magnetic Field, . . . . . .531 



PAGE 



§ 8. The Iron Tubes I. to VII. (Plates I. and II.), . 534 

 § 9. The Steel Tubes I. to VII. (Plates III. and IV.), 536 

 § 10. The Nickel Tubes I. to VII. (Plate V.), . . 538 

 § 11. The Other Permanent Tubes, . ... 540 

 § 12. Complete Cycles and Hysteresis, . . . 542 

 § 13. Behaviour in Fields of Various Distributions, . 546 



§ 7. Method of Experiment, . . . . . 533 § 14. Conclusion and Summary, .... 550 



§ 1. Introduction. — On July 20th, 1891, I communicated to the Society a short 

 note on the effect of longitudinal magnetisation on the interior volume of iron and 

 nickel tubes (see Proceedings, 1890-91, pp. 315-7). These earliest results of observa- 

 tion of a new and interesting phenomenon in magnetic strains were obtained during my 

 last few months' residence in Japan. In following out the lines of research therein 

 suggested, I have been fortunate in having had placed at my disposal by Professor Tait 

 the resources of the Physical Laboratory of Edinburgh University. I desire here to 

 record my great indebtedness to him for the interest he has taken in the work, and for 

 his many helpful suggestions. In surmounting the many experimental difficulties met 

 with at every turn, I had the invaluable co-operation of Mr A. Shand, a senior 

 student in the Physical Laboratory. Various results obtained since 1892 have been 

 communicated in short notes from time to time (see Proceedings, 1891-2, pp. 85-88, 

 249-252; 1893-4, pp. 295-7; 1894-5, pp. 334-5; see also B. A. Reports, 1892 and 

 1893); but it was not possible to regard these as altogether satisfactory. It was only 

 in May of last year (1895) that the many sources of error were finally got rid of, and 

 the apparatus perfected. The present paper deals entirely with the results obtained 

 since then. In these later experiments I was ably assisted by Mr A. C. Smith, a 

 student in the Physical Laboratory. 



A Eoyal Society grant of £50 enabled me to get a series of tubes of iron, steel, and 

 nickel, all very similar as regards external appearance, but differing in diameter of bore. 

 The tubes of any one metal were formed from pieces cut from the same original bar. 

 There were at first five tubes of Swedish iron, five tubes of Bessemer steel, and three 

 tubes of nickel. Another nickel tube was subsequently made from a bar rolled from 

 the same original casting which supplied the first three tubes. Messrs Henry Wiggin 

 and Co., Birmingham, supplied the long nickel bars to order ; and from these the tubes 



VOL. XXXVIII. PART III. (NO. 13). 4 B 



