the route between i and j has to cross a mountain range (stippled). The cost per mile of the route across the plains is much smaller than the cost through the mountains, so that the direct route is not the cheapest. The higher the cost of traversing the mountain area for the greater the refractive index in Losch's analogy) the more the least effort route will be deflected southwards (Figure 3.3B). The final compromise location (Figure 3.3c) will depend on the construction and running costs over the two media of plain and mountain. Let this example seems too highly theoretical, Lisch reminds of the us deflection of a great deal of nineteenth-century trade between the of east coast the United States and California via the Cape Horn route, a diversion which added some 9,200 miles to the direct distance United overland across the States. An equally direct parallel occurs in this with of a century the planning trans-isthmian canal across central America. Of the two major routes considered (the Nicaraguan cut and the Panama cut, the sea distance between the eastern and western United States would been most striking have reduced by the northern route (the Nicaraguan cut) but this saving was insignificant compared to the saving in construction costs on the shorte Panama cut. Again, it is the ratio of the costs that is Had the cost of important. ocean transport been much higher, the advantages of a more northerly route might have been decisive. Since other than United States shipping used the canal, the decision was far less simple in reality, but the basis of Losch's idea remains valid. Specht (1959) has drawn attention to ferry costs and resultant route bending around Lake Michigan, while a small-scale example from the English countryside that makes the point as well is the orientation of bridges across railway lines. Unless a road is of major importance the bridg spans the railway at or near a right angle, deviating from the general direction of the road on either side of the bridge. Lisch would describe this as a result of the very strong refractive or bending power of the bridge-construction costs on the alignment of the route. Similar effects occurred with the construction of Brindley's contour canals in the eighteenth century, such as the Trent and Mersey, and may be. contrasted with Telford's straight cuts such as the