3Where the excise duty on spirits made in a distillery is charged in respect of the wort or wash, the degree of attenuation may be ascertained by reference to the lowest gravity of the wash as declared by the distiller as if that gravity had been found by the officer before its distillation, and accordingly subsection (2) of the said section forty-six shall have effect as if after the words " the lowest gravity of the wash " there were inserted the words " as declared by the distiller or. "