body-work, struts and tubes are to-day taking the semblance of the airship form. Since a balloon when elongated requires to be stiffened to carry the weight of the engine and crew, a light steel girder or frame is often linked up to the gas bag (fig. 1B). This girder does not differ in principle or in the quality of material or type of accessories from the steel aeroplane fuselage sometimes seen in use. The aerial propeller, too, required at the outset the very calculations which we now use for aeroplanes, and thus helped forward the progress of that invention. Most important of all, there is a triplicate relation between the air-resistance of the craft at a particular speed, the power which a petrol engine will provide at a certain rate of rotation, and the power which the propeller can usefully absorb at the same speed; and this relation in the airship is analogous to that in the aeroplane-one of the many facts which made the study of the one an apprenticeship for the other. The neglect of the early airship in England is, more largely than we are aware, accountable for our backwardness in all aeronautics; while it is hardly recognised in France to what an extent the forward position of that country is due to the zeal of Giffard, Renard, Santos Dumont, de la Vaulx and other pioneers of the small dirigible balloon. To-day the airship is not so much uninteresting as eclipsed in interest. That the study of it is not dead is testified to by large orders which are yet being placed in Germany and France for execution this year and next. There is no doubt that money and brains are being devoted to this research abroad; and aeronauts, undeterred by disasters, have achieved singular success within the last few months, notably with the German airship Victoria Luise' and certain Parseval balloons. It is noteworthy that in twelve years of work no Zeppelin airship has sacrificed a single aeronaut; nor have our small English ones, with thousands of miles to their credit. The bulk of the airship, the numbers required to launch it or reharbour it, its loss of hydrogen, involving heavy baggage trains to replace wastage, the insufficient proof of its ability to withstand mooring in the open, form a strong indictment against it. On the other hand, those who have journeyed in airships, as well as those who make them, are far from discouragement. They say that these difficulties are soluble. Once an airship (unlike an ocean steamer, which may meet ice-floes) is clear of the land, there is no power in the wind to upset or hurt it so long as it can ride out the gale; and such staying power is close to our grasp. There are instances of free balloons which have run unharmed for hours in a 60- or even an 80-mile wind; and the extension of this power to airships is simple and legitimate. Airships are now made which rise at 1000 feet per minute and descend without loss of gas or ballast, which can alight where the ground is rough or rocky, or covered with crops, or in small clearings among trees, or in gorse or heather, plough-land or swamps, or during a dark night, whether attendants await them or not; and this makes them available over no small fraction of the earth's surface where aeroplanes would encounter trouble in landing; moreover they can stay out till night, when the air is generally calmest. An airship can hover at a given spot; and the man in charge can with impunity abandon all control and make such written notes or photographs as are necessary. The range of wireless transmission from airships is immense; and, since a dirigible can maintain its level or rise when the throb of its machinery is still, it can receive wireless instructions, and, what is perhaps more important still, obtain the knowledge that its own message has been satisfactorily received, and so continue to transmit useful news. Again, no aeroplane has yet travelled so far as a balloon nor mounted so high or so quickly; nor is it equally independent of air turbulence. For sea-work the airship may yet perform useful duties, since it can come down to the waves with safety, and quit them with great ease. There does not appear to be any reason why a dozen or more of small non-rigid airships should not be packed in the hull of a suitable special ship in attendance on a fleet, and carrying with it the necessary plant for producing gas, as well as devices for mooring in the open; for sufficient experience now exists for mooring devices to be considered practicable. Having given this, which is no excessively optimistic forecast of what may be achieved with the balloon type of craft, we may turn to the other part of our subject, the rationale of practical aeroplanes. Vol. 217.-No. 432, 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 |