Section 66. The commission shall. . . 4. “Have power, in its discretion, to prescribe uniform methods of keeping accounts, records and books, to be observed by gas corporations and electric corporations and by municipalities engaged in the manufacture, sale and distribution of gas and electricity for light, heat or power. It may also in its discretion prescribe, by order, forms of accounts, records and memoranda to be kept by such persons, corporations and municipalities. Notice of alterations by the commission in the required method or form of keeping a system of accounts shall be given to such persons or corporations by the commission at least six months before the same shall take effect. Any other and additional forms of accounts, records and memoranda kept by such corporations shall be subject to examination by the commission.”