= 1, from which the result stated immediately follows.
This transformation is homogeneous and of the first degree in the
. On account of this transformation, the
, are called components of a tensor of the second rank (the latter on account of the double index). If all the components,
, of a tensor with respect to any system of Cartesian co-ordinates vanish, they vanish with respect to every other Cartesian system. The form and the position of the surface of the second degree is described by this tensor (
).