It is possible, with a modern-type compass, to make an allowance for leeway. The airman studies a gauge before he ascends, ascertaining the strength at which the wind is blowing. Then he sets a pointer upon his compass by which he may correct, even while passing through the air, the sideway thrust of the wind; that is to say, should he be flying to some point due east of his starting-point, as was assumed in Fig. 66, and should the wind--blowing from the south across his path--tend to force him towards the north, then he would set his pointer so that he was steering not due east, but to a point a certain number of miles south of east. In this way, with the wind driving him always north, he would arrive not at the imaginary destination towards which he steered, but at the real point due east which he desired to make. The drawback of the method may be this: should the pilot leave ground in a 10-mile-an-hour wind, and should the strength of this wind increase say to 20 miles an hour, his allowance for leeway would be insufficient; but against this may be set the fact that the airman, becoming aware probably, by the increased rolling of his machine, that the wind was tending to strengthen, would steer still wider of his goal. Compasses are being tested, also, which allow pilots to make an accurate and mechanical allowance, even while in flight, for risings or fallings of a side wind. There is one, a form of transparent compass, made so that the airman can look down through it, and see the ground passing away below. Selecting landmarks with his eye which are a little distance apart, he is able to note--by contrasting his compass-course with that his machine makes when in relation with these objects--just how much drift he should allow for. Then he alters his leeway indicator and makes another observation later on, should he think the wind has changed again. [Illustration: FIG. 67.--An Airman’s Map.] Vital to the equipment of a pilot is his map. In the infancy of flying, when airmen first began to venture upon journeys between cities, they had neither maps nor compasses, and contented themselves as a rule with following a railway--the metals of which, gleaming below and appearing as though ruled across the country, provided an excellent guide. But soon, making longer flights and passing perhaps over districts where there were no railways, pilots found they needed a map; but not an ordinary map, such as a tourist upon the earth might use. Flying thousands of feet high, the airman’s view of the land is bird-like. The country stretches away on all sides below, apparently almost flat, and with its hills so dwarfed that they hardly catch the eye (see Plates XI and XII).