A standard of reference for the arrangement of the stars may be had by comparing their distribution to a certain properly modified equality of scattering. The equality which I propose does not require that the stars should be at equal distances from each other, nor is it necessary that all those of the same nominal magnitude should be equally distant from us.

Ch.4 "Life and Works" from a memoir, published (1817). - Sir William Herschel: His Life and Works (1880)