These equations are proved by taking a line fixed in space, whose direction cosines are 1, then dt=mR-nQ,' d'-t = nP =lQ-mP. (5) If P denotes the resultant linear impulse or momentum in this direction P =lxl+mx2+nx3, ' dP dt xl+, d y t x2' x3 +1 **dtl** dt 2 +n dt3, =1 ('+m (dt2-x3P+x1R) ' +n ('-x1Q-{-x2P) ' '= IX +mY+nZ, / (7) for all values of 1, Next, taking a fixed origin and axes parallel to Ox, Oy, Oz through 0, and denoting by x, y, z the coordinates of 0, and by G the component angular momentum about 1"2 in the direction (1, G =1(yi-x2z+x3y) m 2-+xlz) n(y(y 3x 1 x3x y + x 2 x) (8) Differentiating with respect to t, and afterwards moving the fixed.

1 On subtracting from this total the current of establishment of polarization d/**dtl** (f',g',h) as formulated above, there remains vd/dx(f',g',h) as the current of convection of polarization when the convection is taken for simplicity to be in the direction of the axis of x with velocity v.

IavrOUS vW6EQBE [Kai EiSi 7 vETE **dTL** viol 7rarpOS T[.