# Page:LorentzGravitation1916.djvu/24

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${\displaystyle {\begin{array}{c}{\frac {l_{ab4}\lambda _{bc4}}{l_{a}\lambda _{c}}}\chi _{b4}=\chi _{4b}=\psi _{ac},\\\\{\frac {l_{ab4}\lambda _{ac4}}{l_{b}\lambda _{c}}}\chi _{4a}=\chi _{a4}=\psi _{bc},\\\\{\frac {l_{ab4}\lambda _{abc}}{l_{4}\lambda _{c}}}\chi _{ba}=\chi _{ba}=\psi _{4c}.\end{array}}}$

Taking also into consideration the opposite side ${\displaystyle \left(dx_{a},dx_{b},dx_{4}\right)}$ we find for ${\displaystyle X_{a},X_{b},X_{4}}$ the contributions

${\displaystyle {\frac {\partial \psi _{ac}}{\partial x_{c}}}dW,\ {\frac {\partial \psi _{bc}}{\partial x_{c}}}dW,\ {\frac {\partial \psi _{4c}}{\partial x_{c}}}dW.}$

This may be applied to each of the three pairs of sides not yet mentioned under ${\displaystyle a}$; we have only to take for ${\displaystyle c}$ successively 1, 2, 3.

Summing up what has been said in this § we may say: the components of the vector on the left hand side of (10) are

${\displaystyle X_{a}=\sum (b){\frac {\partial \psi _{ab}}{\partial x_{b}}}dW}$

§ 27. For the components of the vector occurring on the right hand side of (10) we may write

${\displaystyle i\mathrm {q} _{a}d\Omega }$

if ${\displaystyle \mathrm {q} _{a}}$ is the component of the vector ${\displaystyle \mathrm {q} }$ in the direction ${\displaystyle x_{a}}$ expressed in ${\displaystyle x}$-units, while ${\displaystyle d\Omega }$ represents the magnitude of the element ${\displaystyle \left(dx_{1},\dots dx_{4}\right)}$ in natural units. This magnitude is

${\displaystyle -i{\sqrt {-g}}dW}$

so that by putting

 ${\displaystyle {\sqrt {-g}}\mathrm {q} _{a}=w_{a}}$ (28)

we find for equation (10)

 ${\displaystyle \sum (b){\frac {\partial \psi _{ab}}{\partial x_{b}}}=w_{a}}$ (29)

The four relations contained in this equation have the same form as those expressed by formula (25) in my paper of last year[1]. We shall now show that the two sets of equations correspond in all respects. For this purpose it will be shown that the transformation formulae formerly deduced for ${\displaystyle w_{a}}$ and ${\displaystyle \psi _{ac}}$ follow from the way in which these quantities have been now defined. The notations from the former paper will again be used and we shall suppose the transformation determinant ${\displaystyle p}$ to be positive.

1. Zittingsverslag Akad. Amsterdam, 23 (1915), p. 1073; translated in Proceedings Amsterdam, 19 (1910), p. 751. Further on this last paper will be cited by l. c.