Other and more elaborate railways in the air have been made in Germany, and there is one for passengers running between Barmen and Elberfield. In this case the single rail is raised on high trestles, and the carriage, which looks very much like a large tramcar, runs along the line suspended beneath the trestles. Then, too, we may in the future have railways that will take us across the English Channel, either through a great tunnel or over a bridge, reaching, as was proposed in 1884, from Folkestone to Cape Grisnez. A third plan that has been suggested for crossing to France is that of a submarine bridge, upon which a curious construction or platform would run, and on this the trains themselves could be taken from shore to shore, while still another proposal was that large ferry-steamers should be built, on the lower decks of which the trains could be carried. And now we will leave the earth and look at the pictures of airships and the wonderful aeroplanes, which, although improvements are being made every day, can already travel at an almost incredible speed and with a security that only a little while ago would have been considered quite impossible. Nowadays air travel is not only a possibility but an accomplished fact, and it is hard to realise that it has come about during the last twenty years, and that before then practical flying machines were unknown. [Illustration: OVERHEAD TROLLEY.] From very early times, however, inventors and scientists have dreamed and experimented, and no less than seven hundred years ago, Roger Bacon, one of the most learned men of his day, seems to have looked down through the centuries and to have actually seen the aeroplanes with which we are now familiar. "There may be made a flying instrument," he says, "so that a man sitting in the midst of the instrument and turning some mechanism may move some artificial wings so that they may beat the air like a bird in flight." It was a strange prophecy, but in those far-off times--the dark ages we call them--men had already fixed their hopes on flight, and school children were trained in the use of wings as in that of the globes. We are not told what advantages this curious accomplishment gave to the little boys and girls of the thirteenth century, and, indeed, it may have brought them ill-fortune, for in those days inventors were often accused of witchcraft, and new ideas were looked upon with suspicion. Even centuries later, when the first balloons were causing great excitement in England, many people thought that it was wrong to spurn the laws of nature by attempting to fly. [Illustration: MONOPLANE, THE FIRST TYPE TO CROSS THE CHANNEL.]