# Page:Aether and Matter, 1900.djvu/199

 ${\displaystyle 4\pi {\frac {d}{dt}}(f,\ g,\ h)=curl\ (a,\ b,\ c)}$ ${\displaystyle -{\frac {d}{dt}}(a,\ b,\ c)=4\pi c^{2}curl\ (f,\ g,\ h),}$
in which the symbol ${\displaystyle curl\ (a,\ b,\ c)}$ represents, after Maxwell, the vector
${\displaystyle \left({\frac {dc}{dy}}-{\frac {db}{dz}},\ {\frac {da}{dz}}-{\frac {dc}{dx}},\ {\frac {db}{dx}}-{\frac {da}{dy}}\right),}$