In 1809 Sir George Cayley wrote articles on flight, indicating the use of curved aerofoils; and in 1810 the artist Walker, of Hull, published diagrams of gliding models, which do not differ much from the best model aeroplanes of to-day. There can be no question that they glided well. The difficulty was to get an adequate source of power, so that the gliding should be continued and therefore constitute flight.' The first to make an enginedriven aeroplane which flew was Stringfellow, in 1848. Curiosity is naturally aroused by the names of the men who first invent a device so remote from utility in their day, but it is well to remember that it is equally difficult and equally creditable to invent it again independently. This seems to have occurred over and over again with aeroplanes, since the apparatus made, having no commercial value that could be appreciated without a considerable use of the imagination, fell into oblivion as soon as the inventor passed away or lost the first fervour of his zeal.

At first, our neighbours, the French, were in the rear in regard to these inventions. No organised activity like the Aeronautical Society (founded in 1866) appears to have been afoot in France; and, though the bat-like wing structure of Ader's Avion (1890) re-appeared in Germany on Lilienthal's glider (1891), and in England in Pilcher's modification of it which he called his 'Hawk' (1895), the aerodynamic value of both the German and English machines was superior to the French one, in so far as they carried their designers most successfully, while the Avion did not. This situation has been fully, too fully, modified by the superior progress of the French in later years. Yet we are glad to look back to a brief moment in that rudimentary stage at least, when we seem to have been ahead of the French both in forming our scientific organisation and in effecting flights. The writer recalls with pleasure that in 1892-3 he was privileged to be a passenger in some flights in Hiram Maxim's steam-driven aeroplane, the like of which was certainly not available on the Continent. This was, amongst other things, a most strenuous attempt to tackle the second of the great flight problems of the day, that of propulsion. The aeroplane was capable of flying, and free to fly, but not to rise above a limited level from the ground-a pair of top rails, beneath

which the aeroplane ran, having been arranged along the course to prevent this. A fortunate accident, by which the aeroplane got away from its restraining rails, gave Maxim his early position on the list of free flyers in engine-driven aeroplanes.

But our pride in Cayley, Phillips, Stringfellow and Pilcher cannot blind us to the fact that the work of two Americans, Wilbur and Orville Wright, is the startingpoint of the modern self-propelled flying apparatus. We may, however, note with gratification that Wilbur Wright, whose death we so recently have had to deplore, quoted Lilienthal, Pilcher and Chanute as the three experimenters whose methods of gliding were of use to him. Of the three problems of flight-the building of wings, the designing of propelling machinery, and the balancing and steering-it was in the last that he treated them as his teachers; and it was from that stepping-stone that he made his great advance-wing-control for the purpose of balance.

This

To realise the difficulty of obtaining this balance, it is necessary to grasp the fact that the velocity of wind varies to an amazing degree. Some idea of its irregularity may be gained from the wavy lines in fig. 2, taken in March this year at 35 feet from the ground. In this the crests of the waves indicate increase of wind-speed in miles per hour, and the hollows represent partial lulls. particular curve is interesting, both because the analysis is carried to a considerably finer degree than usual, and also because it was arranged that a pilot should fly in the wind of which this is the record. The curve shows some twenty-seven changes of wind-speed in the minute. Flyers know that the balancing lever in the pilot's hand was feeling these impulses, and beating to and fro in countering their disturbing effect. The greatest wind was measured at 30 miles per hour during the fourth minute at the level of the measuring gear 35 feet up; but from this it is not possible to know what the wind was at the higher levels, above 900 feet, where flight is more safely to be practised. Other experiments have shown that on similar days the upper wind may have had a speed of some 50 miles per hour.

The accurate analysis of wind-speeds at levels such as 1000 feet is possible in France, but not so in this country,

because we have here no Eiffel Tower; and it would be well if this deficiency were remedied. All we can do, as a rule, is to make an estimate of the general windspeed, whenever we see that an aeroplane is battling through the wind without advancing over the ground. Thus Mr Hamel recently rose to some 6000 feet on a Blériot (April 6, 1912) in a wind which was recorded as 20 to 25 miles per hour at the top of a 25-foot mast. This was proved to be 65 miles an hour at the greater height, because the aeroplane, whose speed was known to be 65 miles per hour, remained stationary for a long period of time when facing it.

The practical interest of this digression is that it enables us to be more tolerant of the conflicting statements so commonly published about wind-speeds at the time of flight, since the level at which the wind measurement was made is rarely or never given. As we rise higher into the air the small pulsations indicated in fig. 2 become less frequent, at any rate in England. The 300-yard level line roughly follows the profile of the earth's surface; and the winds below that level behave generally in a similar way, save that winds attaining a certain degree of velocity-say 20 miles an hour-dash through and past aerial obstacles till they are raised vertically on the windward side of any long range of hills. The impression given is that such a range of hills causes a vertical deflection of a body of the air some 2000 yards thick before the hill is reached; and the vertical movement of a 20-mile wind extends to a height of 1000 yards above the hills.

It is thought by Captain Ley, a serious experimenter on the subject, that there are certain dividing planes or levels or stages other than the 300-yard level where special irregularity may be met with in England, namely somewhere about 700 yards up, 1000 yards up, and 1300 yards up. These divisions apparently occur at the top of the air-zone dominated by the plains, the hill-ranges, and the mountains respectively; and at these dividing planes there are disturbances and sudden changes of wind-speed. Obviously down-draughts are to be expected on the sheltered side of hills, and special oscillations above a lake or at the margin between land and sea, the latter requiring without doubt very special study from that