I had a chance yesterday to check a copy of the first edition -1949 - of the
Margenau, Watson and Montgomery text "Physics, Principles and Applications".
In their Preface they write "Our outlook, we believe, is fairly modern. In
electromagnetism the exposition recognizes that the forces between charges,
at rest and in motion, are fundamental, and hence magnetic poles take on
minor significance in this book." (page vi)
In the body of the text (page 390), they write " The strength of the
magnetic induction can be defined (written in italics) by the force that is
exerted on a moving charge."
A point that I am wondering is what was the first introductory book to call
B the magnetic field rather than the magnetic induction. Any suggestions?