In these regions there is no dust in the air to diffuse the light and the air is dry and consequently excellent for persons with lung trouble. There is even a possibility that physicians will advise patients suffering from tuberculosis to ascend to these high altitudes, and it is a fact that Hubert Latham was threatened with this disease, yet enjoyed good health after taking up aviation, only to be killed by a wild buffalo, as related. Perhaps this is one of those cases I was looking for where the aeroplane has saved a life. METEOROLOGY An aeroplane will bring quick reports of changes in the weather. Rapid investigations of conditions which exist in the strata of air at varying altitudes above the surface of the earth, made by the use of flying machines, may lend us material aid in understanding those conditions which are closer to earth. The study of the weather and meteorological conditions becomes of greater and greater importance as the progress in the science of aviation advances. The currents of air that are regular in their direction of movement, like the trade winds, must be mapped and charted, for with the aid of a strong wind an aviator can make marvellous speed, as the speed of the wind is added to the speed of his machine and with an aeroplane capable of making one hundred miles an hour a favourable wind of fifty miles an hour would increase the total speed by one half. For the wind is now no longer an obstacle to flight, and as I have already noted at the beginning of this chapter, this is one of the most noticeable advancements in aviation, one that can readily be seen, understood, and appreciated even by the uninitiated. THE TENDENCY TOWARD HYDROS There is always more or less danger in flying over land, and the rougher its surface the more difficult and dangerous the matter of landing. The safest place and the most uniform surface is to be found over the water, and there is much less danger to the aviator flying there than over the land. The strength of the wind can be easily judged by the height of the waves, and squalls and puffs can be seen coming so that if they seem to be very bad you can come down on the surface of the water or skim along very near it with the greatest safety, if you are in a hydroaeroplane. Rivers will no doubt become the favourite highways of travel for the airman, as they were once the only great avenues for the march of civilisation when the canoe or the rude boat was the only vehicle of transportation. This brings us naturally to another consideration of the air-land-water machine. CHAPTER III THE FUTURE OF THE HYDRO