M. HANREZ' proposed “waiting carriage” (NATURE, xxii. 519) has doubtless been schemed by many readers before now. A simpler form had long ago occurred to me, having the drum of cable in the train engine, the cable passing under the carriages and catching the waiting carriage at the tail. The running out of rope could be as well managed at one end of the train as at the other, and only an ordinary carriage without any special engine would be required, which would be dropped just before picking up another at the next station, each carriage thus slowly shifting round the line.