Mechanical traction will also help effectually in handling airships on the ground, and the difficulty of taking them in and out of sheds has always been unduly magnified. The provision of track rails and travellers to which the guys of the ship can be attached, as is the practice in Germany, will tend to eliminate the source of trouble. We must now consider the effect that weather will have on the big airship. In the past it has been a great handicap owing to the short hours of endurance, with the resulting probability of the ship having to land before the wind dropped and being wrecked in consequence. Bad weather will not endanger the big airship in flight, and its endurance will be such that, should it encounter bad weather, it will be able to wait for a lull to land. Meteorological forecasts have now reached a high state of efficiency, and it should be possible for ample warnings to be received of depressions to be met with during a voyage, and these will be avoided by the airship flying round them. In the northern hemisphere, depressions generally travel from west to east and invariably rotate in a counter-clockwise direction with the wind on the south side blowing from the west and on the north side blowing from the east. Going west, the airship would fly to the north of a depression to take advantage of the wind circulating round the edge, and going east the southern course would be taken. Lastly, the vulnerability of the airship must be taken into account. Hydrogen is, as everyone knows, most highly inflammable when mixed with air. The public still feels uncomfortable misgivings at the close proximity of an immense volume of gas to a number of running engines. It may be said that the danger of disaster due to the gas catching fire is for peace flying to all intents and purposes negligible. At the risk of being thought hackneyed we must point out a fact which has appeared in every discussion of the kind, namely, that British airships flew during the war some 21 million miles, and there is only one case of an airship catching fire in the air. This was during a trial flight in a purely experimental ship, and the cause which was afterwards discovered has been completely eliminated. For airships employed for military purposes this danger, due to the use of incendiary bullets, rockets and various other munitions evolved for their destruction, still exists.