Practically the only accurate method of making any such computations is to study the entire territory which will be served by the road and estimate in detail the amount of business which will be obtained from every manufacturing plant, mine, lumber-camp, and even every farm. Through country districts and through towns which are not already served by a railroad such an estimate is not very difficult. Generally the errors will be on the safe side, unless rendered valueless by a gross exaggeration of the expected increase in business. A factory which can do business without railroad facilities will frequently multiply its business many times when it is connected with the outside world by a railroad which passes its doors. It is usually safe to estimate a freight-charge not only on the entire present output of the factory, but to even consider that the factory will grow and furnish a much larger amount of business. An experienced estimator will soon estimate the probable yield of the farms which are within five miles of the road and what would be the probable market for the produce when it became possible to ship it by rail. In estimating what farms should be thus included the distance from the farm (perhaps in an opposite direction) to another railroad and also the nature of the roads and the hills should be taken into consideration. It is usually possible to predict with certainty that a farmer who had previously hauled his entire output over a steep hill for a distance of seven or eight miles to an existing road will transfer his entire business to the new road because the new road will be only three miles away and the grade is downhill. It may even be justifiable to consider that the farmer will produce more of certain kinds of crops, since the accessibility to the markets produced by the proposed road will encourage him and will enable him to make profits which were anobtainable before. Of course the estimator must have sufficient knowledge of mercantile values to know what are the probable markets, not only for farm-produce, lumber, and minerals, but also for manufactured products. The estimator will consider each proposed station on the road in turn and will estimate (considering first the freight business) that the farms within reach of that station will annually bring to that station so many tons or car-loads of various kinds of farm-produce which will probably be shipped to a certain market, or at least will be shipped from that station to one or the other of the termini of the road where they will connect with other lines. Multiplying that tonnage of produce by a suitable freight-rate for the distance will determine the receipts for those items. Each lumber tract, each mine and each factory should be considered in the same way. Unless there is some place along the line where certain products are consumed the traffic of this kind will usually run from the local station to one or the other of the termini. Of course there will be a small amount of local freight traffic between stations along the line, but this is usually a comparatively small proportion of the business done.