296 MOTIVE POWER EMPLOYED

Having thus given as minute a descriptionof Rail-roads, and the ditFerent kinds of motivepower employed upon them, as my timeand the extent of my researches permit, itmay not be uninteresting to give a sort ofbrief outline of single and double lines ofroad, with their passings, as they may berequired for the general conveyance of goods.

In most of the Rail-roads in the neighbour-hood of Newcastle-upon-Tyne , and otherdistricts of Great Britain, which I have visited,one main line of road is laid the wholedistance, with short pieces of double road atcertain intervals, and proper passings betweenthem, for the carriages going in one directionto pass the others returning in the oppositedirection. In public lines, and for generaltraffic, perhaps, in many cases, double linesof road the whole distance may be preferable:but this will, in all instances, be regulated bythe peculiar circumstances of each particular lineof road. Dividing them into two kinds, viz.single lines with different kinds of passings, anddouble lines with common passings from oneto the other.

Fig. XII. Plate II. will represent adouble road, with the crossings from one lineto the other, for the carriages to pass each