He proposed that electromagnetic - radiation waves were carried by the ether and that magnetic lines of force were disturbances of the ether. (phy.pmf.unizg.hr)
A compass, by contrast, follows magnetic lines of force and often errs badly. (discovermagazine.com)
The x-ray flare is large in extent, has fine strulctuire, and follows a neutral magnetic line. (science.sciencemag.org)