. The tensor character indicates that the equation of transformation is
Tensors may be formed by the addition and subtraction of tensors of equal rank and like character, as in the theory of invariants of orthogonal linear substitutions, for example,
The proof of the tensor character of
depends upon (58).
Tensors may be formed by multiplication, keeping the character of the indices, just as in the theory of invariants of linear orthogonal transformations, for example,
The proof follows directly from the rule of transformation.