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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1918 Excerpt:...have blown from a certain direction for some time they do not give conclusive evidence of the direction of the pressure gradient, owing to the susceptibility of light winds to local topography and diurnal change in temperature. Judgment will therefore often have to be deferred until the behavior of the first kite has been observed. With a little practice, conclusions concerning the pressure distribution can be arrived at agreeing quite closely with that subsequently shown on the weather mat). This refers more particularly to the cold season, when pressure conditions and changes are sharply denned. With approaching warm weather the whole problem of analyzing pressure conditions becomes increasingly difficult, and one will often be at a loss to know what to expect. This has its compensations, however, in the comparative freedom from unsafe conditions (except such as are of a local nature) in summer weather. The trend of the isobars can be approximated by considering the direction of the wind at that moderate altitude above the ground where surface friction is surmounted and to which the kites gradually veer. Abrupt changes in wind direction have causes other than surface friction. In Lows and in the rear of Highs gradient winds will be found at only a few hundred meters above the ground. While their direction with reference to the isobars varies somewhat with the rate of movement of the Low or High and their depth varies enormously in different quadrants, it is sufficient to know that the direction of these gradient winds is approximately parallel to the surface isobars, with low pressure on the left. Above these gradient directions the winds in a low will ordinarily veer or back to the higher levels in which the Low seems to move, depending on whether the Lo...