( 631 ) 



XXVI. — Magnetic Shielding in Hollow Iron Cylinders and Suj)erposed Inductions 

 in Iron. By James Russell, F.R.S.E. (With Six Plates.) 



(Read February 3 and July 7 and 21, 1902. Issued separately April 21, 1903.) 



CONTENTS. 



SECTION 



1-2. Introductory, 



3-4. Objects of Investigation — I. Shielding ; II. 

 Superposed Inductions ; III. Magnetic 



^Eolotropy, 



5-7. Apparatus and Experimental Methods, 

 8-9. Theoretical Shielding Ratios, 

 10-13. I. (a) Shielding Ratios with Transverse 

 Field only, . .... 



14-29. II. Superposed Magnetic Inductions, 

 14-21. (a) Increasing from Zero, . 



22-29. (b) Cyclic Conditions, 



30-37. III. Magnetic iEolotropy of Demag- 

 netised Iron, ..... 

 38-52. T. (/)) Shielding Ratios with Transverse 

 and Circular Fields, . 

 38. Classification of Field 



Superpositions, 

 40. Stefan and Du Bois 



Results, 



PAGE 



631 



SECTION 





39-42. 





43-47. 



632 





633 



48. 



635 



49. 





50. 



637 



51. 



639 



52. 



639 



53-56. 



644 





649 





654 





654 





655 





Paqk 

 I. (b) Shielding Ratios — continued. 



Experimental Shielding Ratios, . 654 

 Co-ordination with Magnetic 



Induction, .... 657 



Conclusions under TC conditions, 661 



CTT „ . 662 



CT „ . 663 



TCC „ . 664 



„ Cyclic „ . 665 



53-56. I. (c) Shielding Ratios with Transverse 



and Longitudinal Fields, . . 666 

 Summary. 



§§ 1, 3, 5-13 and 38 to 52, communi- 

 cated 3rd February 1902. 

 §§ 2, 4 and 14 to 33, communicated 



7th July 1902. 

 >?§ 34 to 37 and 53 to 56, communi- 

 cated 21st July 1902. 



Introductory. 



§ 1. The shielding effect which exists within hollow iron spheres and cylinders, when 

 placed in a uniform magnetic field, has been previously investigated. Poisson, 

 Stefan,* Maxwell, and among others, and more recently, Professors Rucker t and Du 

 Bois,| have contributed to the subject. If 



External Magnetic Field 

 ^ ' Internal Magnetic Field 



n — thickness of the shell 



K = outside radius, 



and the ratio of n to R be of the order of ] to 100, it appears that the following 



expressions may be taken as sufficiently correct : 



2 d 

 g -l = — -jj(w-2) (sphere) 



g-l = — ( tt -2) (cylinder). 



* Wied. Ann., xvii. p. 928 (1882). 

 t Phil. Mag. (5), vol. xxxvii. p. 95 (1894). 



I Electrician, " Magnetic Shielding," vol. xl. pp. 218, 316, 511, 652, 814, and vol. xli. p. 108 (1897-98). 

 TRANS. ROY. SOC. EDIN., VOL. XL. PART III. (NO. 26). 5 a 



