Page:A Treatise on Electricity and Magnetism - Volume 2.djvu/52

We shall consider Austral magnetism, that is, the magnetism of that end of a magnet which points north, as positive. If we denote its numerical value by m, then the magnetic potential

$V=\sum {\left({\frac {m}{r}}\right)},$

and the positive direction of a line of force is that in which V diminishes.