Approval of the method proposed by the utility of determining depreciation of its underground plants only represents approval of one means of presenting the evidence as to depreciation in the valuation of part of the inventory. It is a matter primarily within the discretion of the commission in the first instance, and, if the commission abuses its discretion, such abuse can be urged if necessary in an appeal from the final determination of the commission.

The order in this case is purely of a preliminary nature. No other action has been taken in this case. This order, in view of the limitations as to its use as evidence, affected no substantial rights of the parties and is, therefore, not a final order from which an appeal can be taken.

The motion to dismiss is sustained.

Appeal dismissed.