The "Chemin de Per Glissant," or Gliding Railway.
Engineering News—October 26, 1889

In our issue of Aug. 31, a Paris correspondent gave to our readers sketches and an excellent general account of this novel and promising method of propulsion on railways now in operation in Paris. We supplement this article by some further detail from Le Génie Civil of Sept. 28, and reproduce from that journal a perspective view which will better illustrate the general appearance of this new hydraulic motor than anything we have given before.

The description of the operation already given was so complete that we will only supplement it by giving some further collateral data.

Among the first objections that are naturally made against the method of M. GIRARD is the effect of cold upon a system which rests entirely upon the use of water. M. BARRE, the engineer, answers this objection as follows: As all the liquid used in the various parts of the machine is carefully gathered again for re-use, it is believed that a regular service can be maintained in the climate of France by a mixture of water with one-fifth part of glycerine. Even admitting that the total loss would reach 1 per cent., the loss of glycerine would only be 0.2 per cent. In place of glycerine the chloride of magnesium may be used; the latter is cheaper than glycerine and does not attack metal. A proportion of 1 of chloride to 7 of water would be sufficient.

If it is preferred to use the water alone, it would be necessary then to protect, by non-conducting covering, the accumulators and propulseurs, or motor jets. In the case of an elevated metallic roadway these parts could be covered by wooden casing placed between the girders. The reservoirs for the pumps could be arranged in such a manner as to be heated in winter. With a temperature of 5 degrees Fahr., for example, it would only be necessary to raise the water to 61degrees Fahr. to permit the whole apparatus to lie idle for 20 hours before the temperature would fall to 32 degrees. The thin sheet of ice which would form on the sides of the "rail," as it may be called, would be melted, and removed by the water of the following train. The only precaution necessary would be to detach the patins, or slides, from contact with the rail after a long stop by circulating through them for a few seconds a jet of steam before moving, from the heating apparatus of the cars or otherwise In the case of a line located upon the ground, the apparatus of propulsion would be enclosed in a gallery placed either under the road or at the sides.

As the movement of trains thus propelled is extremely easy and produces no shock, it is alleged that the roadway may be placed directly on the ground without any kind of ballast. [We doubt this.-ED.] This feature, coupled with the ability to ascend steep grades and pass around curves of short radius, enables the engineer to practically follow the natural surface and to make the actual construction very economical. The speed of these trains is very considerable. There is no economical purpose in reducing it for certain classes of traffic. In the case of curves, the friction is no greater than on a straight line, for the trains reach the curves always with the same velocity, and the rails can be so inclined as to entirely destroy the centrifugal force,—a result which cannot be reached in a combination of rails and wheels.

The important claim is justly made that in the cases of water power of great volume and force found so often in mountain regions, the expense of traction will be little more than that of selecting and leading this power to the machine.

The advantages of the system are summed up by M. BARRE as follows: (1) Ease of motion; no shaking and no lateral movement. (2) No noise, dust, or smoke. (3) Derailment impossible, as no foreign body can get under the shoes. (4) An almost instantaneous stop without shock; as a consequence collisions may be easily avoided. (5) Ease in ascending steep grades and passing around curves of short radii. (6) A velocity touching 124 miles per hour, with a pressure of 22 kilos. (313 lbs. per sq. in.) in the supplying conduit. (7) Lightness of material in roadway, and consequently economy in construction. (8) Considerable economy in the expense of traction and in the weight and cost of carriages. (9) Notable economy in repairs in the motive power. M. BARRE estimates this latter item as being equal to 66 per cent., on account of the reduction in the number of horse power necessary to operate this machine, and because proper pumps for compressing water move slowly and are not subject to the excessive shaking and speed of moving parts incident to a locomotive in operation.

M. BARRE claims that the obstacles to the system are included in the expense of the first plant, the providing of considerable quantities of water, the action of cold, etc.; not counting the obstacles as yet unforeseen which may arise in practice. He claims that it is as easy to provide for the proper supply of water to each shoe in use as it is to be assured of the proper behavior of each wheel under an ordinary railway train.