It must be remembered that, in estimating the operating expense and income of the starting plant, as well as the going plant, the figures must be confined rigidly to the plant as it is found at the date of valuation, and in no case should any account be taken of income or operating expenses due to probable future extensions of the distribution system. Many appraisers overlook this point, and predicate the anticipated profits of the going plant on the past growth of the income account, forgetting that a considerable portion of this growth is due to extensions into new territory, and not to any material increase in revenue from the territory already served. To include income from new territory in the forecast of income is just as fatal an error as to include the anticipated expenditure of new capital in the present physical valuation. Either of these procedures is really an estimate or appraisement of some other plant, rather than the one actually under consideration. To complete the numerical illustration, suppose it is determined that the time required to construct the hypothetical starting plant is 3 years; that a portion of the plant is put into operation at the end of the second year, taking over fire-hydrant rental equivalent to $20,000; that the revenue from private sources aggregates $20,000 during the last year of construction; that the expenses of operation, maintenance, taxes, and depreciation amount to $30,000 during this year. After the time of completion of the plant has elapsed, it has the total credit for fire-hydrant rental, and it is assumed that the revenue from private sources and the cost of operation, maintenance, taxes, and depreciation increase as shown in Table 14, which illustrates the method of computing the going value, and gives the resulting value for the case just stated. Therefore, 171,005 + 0.2597_x_ = _x_; hence, _x_ = $231,000. This result is based on the assumption that the starting plant earned no interest during the construction period. If an allowance for lost interest during construction has been made and added to the capital account already being included in the physical appraisement of $1,000,000, then this must be charged back against the going value found above. This is clearly evident, because the calculations to determine going value date from the beginning of the construction period, and the lost interest during construction, therefore, is provided for in the result. Most appraisers allow an item for lost interest amounting to the legal rate of interest running for half the construction period, which, in the illustration under discussion, would be $90,000; deducting this sum, if previously included, gives $141,000 as the going value.