This lamp acts on precisely the same principle. A bellows is attached to the brass tube. This bellows the signaller works, either in short or in long pressures; and the air, as it passes up, goes through the powder and forces a small quantity of it through a pair of nozzles placed close to the spirit-flame. The result is a brilliant flash, which is long or short according to the pressure upon the bellows. This light can be seen at a very great distance, and two or three parties of signallers placed upon hill-tops could convey an order a distance of fifty miles in a very few minutes. The difficulty, of course, lies in the liability to error. A single puff more or less might entirely change the order. 1021 might mean “Concentrate upon your left flank;” 1022 “Concentrate upon your right.” It is all very well to say that each signal is repeated, and therefore that a mistake would be instantly corrected; but we all know what mistakes occur in telegraphic messages, even if we pay for their being repeated. The system appears as good and as little liable to error as anything of the kind could be; but when we consider that a miscounting of the flashes of light or of the waving of a flag might entirely alter the order given, it is evident that the risk is so great that a general would rather, if possible, despatch a mounted officer with written instructions. At the same time, the system for distant communication is undoubtedly adapted to expedite the movements of an army over a large tract of country. General Napier has taken a great interest in the experiments, and I have no doubt the system will be thoroughly tried during the present expedition. The apparatus for each signalling-party is singularly complete and handy; it is carried in two baskets or mule-panniers, and includes everything which could be required, comprising a light-tent, a canteen, flags, lanterns, a supply of alcohol and powder, a small case for writing in the rain, signal-books, &c. Each of these double panniers contains, in fact, everything required for the signalmen; and with twelve such apparatus, distributed among parties placed upon hill-tops, signals might be flashed at night from London to Edinburgh.