Robison's Manual of radio telegraphy and telephony for the use of naval electricians (1918)
Robison, S. S. (Samuel Shelburne), b. 1867, United States Naval Institute, Todd, David Wooster, Hooper, Stanford Caldwell · Annapolis, Md. : The United States Naval Institute · leaf 26
=g^ unity, and on that basis the permeability of the purest wrought iron is3,000. In other words, within limits the same current will produce 3,000times as many lines of force in iron as in a body of air of the samelength and area of cross section. CURRENT … -< c ->- D Fig. 14. 26. If the iron of fig. 14 is extended to include C D, as in fig. 14a, theeffect of changes in A B is increased still more, because in fig. 14 thelines of force are partly in iron and partly in air, while in fig. 14a theyhave an iron path throughout, and are consequently…
