(41) The invariance of the equations

with regard to the group of cyclical substitutions,

and the consequent invariance of the eliminant with regard to the reduced group consisting of the last two substitutions, has been already referred to. When the eliminant is expressed in terms of the three-line determinants formable from the array of coefficients, the invariance in question is self-evident, as each of the twenty-eight parts composing the expression is invariant by itself. For convenience this form may be repeated from § 31 with a slightly improved notation.