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 17
Fig. 6. Fig. 7. as sliown in fig. 6. Some force connected with the magnet must makethe filings assume these positions, which are different from what theywould be if the magnet was not under the paper; and from the way thefilings are arranged, this force must act in the space surrounding themagnet.…
