wind is strong a landing should not be attempted in any such place. If forced to land in a place of this kind the machine should be headed along and not at right angles to the direction of the hill.
4. Aerial Torrents.—Steep barren valleys, especially of clear still nights and when the upper reaches are snow covered, are the beds of aerial drainage rivers that at times amount to veritable torrents. Therefore however quiet the upper atmosphere and however smooth its sailing, it would be extremely dangerous to attempt to land an aeroplane at such a place and such a time.
All the above sources of danger, whether near the surface like the breakers, the torrents and the eddies, or well up like the billows and the wind sheets, are less and less effective as the speed of the aeroplane is increased. But this does not mean that the swiftest machine necessarily is the safest; there are numerous other factors to be considered and the problem of minimum danger, or maximum safety, if the aeronaut insists, can only be solved by a proper combination of theory and practise, of sound reasoning and intelligent experimentation.