I'm reading the article above and have a question in "3.5.1 A History of Magnetostatics". I wonder what magnetic field is. So I started reading 3.5.1 and don't understand how Jean-Baptiste Biot and F´elix Savart determined the strength of the magnetic field. Explanation above it just shows experimental phenomenon. Where does the 'strength' of magnetic field come from?? Please don't just say maxwell's equation or lorentz force. I want to know about historical flow.