Although it is possible to insulate the rails in a satisfactory manner in the case of an elevated road, the conditions of insulation are not very favorable where the railway is to be constructed on a level with the surface. In this case it becomes necessary to dispense with the simple and cheap arrangement of rails as conductors, and to set up, instead, a number of poles to support the electric conductors. It is from these latter that certain devices of peculiar construction take up the current. The simplest arrangement to be adopted under these circumstances would evidently be to stretch a wire upon which a traveler would slide--this last named piece being connected with the locomotive by means of a flexible cord. This general idea, moreover, has been put in practice by several constructors. In the Messrs. Siemens Bros.' electric railway that figured at Paris in 1881 the arrangement adopted for taking up the current consisted of two split tubes from which were suspended two small contact carriages that communicated with the electric car through the intermedium of flexible cables. This is the mode of construction that Messrs. Siemens and Halske have adopted in the railway from Frankfort to Offenbach. While the Paris road was of an entirely temporary character, that of Frankfort has been built according to extremely well studied plans, and after much light having been thrown upon the question of electric traction by three years of new experiments. Fig. 1 shows the electric car at the moment of its start from Frankfort, Fig. 2 shows the arrangement of a turnout, and Fig. 3 gives a general plan of the electric works. [Illustration: FIG. 1.--THE ELECTRIC RAILWAY, FRANKFORT, GERMANY.] The two grooved tubes are suspended from insulators fixed upon external cast iron supports. As for the conductors, which have their resting points upon ordinary insulators mounted at the top of the same supports, these are cables composed of copper and steel. They serve both for leading the current and carrying the tubes. The same arrangement was used by Messrs. Siemens and Halske at Vienna in 1883.