Magnetic Permeability of various Alloys of Iron. 



69 



stamped on each specimen so as to avoid mistakes and facilitate reference. 

 These marks also give some indication of the history of the specimens : thus a 

 series of similar numbers but with different letters attached, e.g. 1167 D, 1167 H, 

 11671, tell us that it is the same batch of "steels," with different joroportions of 

 the added element or elements : — 



Class I. 



No. of 

 Group. Description. Specimens. 



1. Carbon steels, 13 



2. Manganese steels, ...... 18 



3. Nickel „ 12 



4. Tungsten ,, 4 



No. of 

 Group. Description. S/jecimens. 



5. Aluminium steels, 3 



6. Silicon ,, 2 



7. Chromium ,, 3 



8. Copper ,, 4 



Class II. 



Group. Description. 



9. Nickel — Copper steel, 



10. ,, Chromium steels, 



11. ,, Silicon ,, 



12. „ Manganese ,, 



13. Manganese — Chromium steels, 



14. ,, Tungsten ,, 



15. ,, Silicon ,, 



No. of 

 Specimens. 



1 



6 



5 



9 

 4 



4 

 2 



Group. 



16. 

 17. 

 18. 

 19. 

 20. 

 21. 

 22. 



Description. 

 Manganese — Copper steels. 

 Chromium — Aluminium steels 



,, Silicon ,, 



,, Copper steel, . 



,, Tungsten ,, 



Aluminium — Copper ,, 



,, Silicon ,, 



No. of 

 Specimens. 



Class III. 



No. of 

 Group. Description. Specimens. 



23. Cobalt — Manganese — Silicon steels, 2 



24. Nickel — Manganese — Copper steel, 1 



25. Chromium — Tungsten — Copper ,, 1 



26. Chromium — Manganese — Silicon ,, 1 



Group. 



27. 



28. 



No. of 

 Description. Specimens. 



Nickel — Manganese — A lumin ium — 

 Silicon steel, 1 



Copper — Manganese — Chromium 



steel, 1 



PART I. 



Electrical Conductivity. 



Method of Measurement. 



As the rods were about half a centimetre diameter and a little over a metre 

 long, the ordinary method of determining the resistance was unsuitable ; accord- 

 ingly the potential method of measuring conductivity was employed. Each 

 specimen was compared with a standard of pure copper, of high and known con- 

 ductivity, and also subsequently with a standard iron rod, of the purest com- 

 mercial iron obtainable. A complete analysis of this standard iron (an excellent 



M2 



