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
s of force created with thesame current is very greatly increased. MANUAL OF RADIO TELEGRAPHY AND TELEPHONY. 21 This shows that it is easier to create lines of force in iron than in air;or, to state the fact differently, lines of force permeate iron more easilythan they do air. The relative ease… … =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
