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it, may be summarized as that, in his opinion, (1) aerial navigation is not likely in the near future to become of such importance as seems generally supposed, and (2) that whatever utility may be accomplished in this line will be due to the propelled balloon rather than to the dynamic flying machine. I venture to take a diametrically opposite view, and shall attempt to show that it is likely to form a problem of the very highest moment to Englishmen, and that this will result more particularly from the introduction of the "flyer." I have reason to hold more decided views on the matter now, for since reading the article I have had an opportunity of travelling some miles through the air in the marvellous machine of Mr. Wilbur Wright. Such an experience is calculated to prejudice one strongly in favor of this means of transport, and to make one realize what a vast future there is before us in the realms of the air. To sit in a comfortable seat, and, without effort, free from any jolting or unpleasant motion, to be wafted through the air. at forty miles an hour, with a regularity and certainty which is surprising, gives one food for reflection indeed. The feeling of safety which this clever and experienced aeronaut inspires in one displaces all fear of danger.

In order to discuss the first of the conclusions it will be necessary to have in mind some idea of the means by which the air is to be navigated, and this makes it necessary to begin by considering the latter of the two statements, that is the asserted superiority of the propelled balloon over the "flyer."

First let me explain that in disparaging the poor old airship, which in the past I have so often extolled, it is only to show that the flying machine is preferable; the gas-bag is useful enough if we have nothing else with which to navigate the air.

A balloon must be very large. It is sometimes forgotten by inventors and others that the whole principle of the ascent depends on the displacement of the air. A balloon must be of such a volume as to displace a mass of air more or less equal to its entire weight. Air weighs about 76 lbs. per thousand cubic feet. So, no matter how light the materials used or how ethereal the gas, the apparatus must have a bulk of over a thousand cubic feet for every 76 lbs. that is required to be lifted. But great bulk implies two drawbacks. It must offer great resistance to propulsion, which necessitates powerful engines to drive it at any speed through the air, and speed is all-important in aerial navigation.

The second drawback to great bulk is the difficulty in housing the apparatus when on the ground and protecting it from strong winds and weather.

Then the material of which a balloon is made must be costly. It must be very light, and is therefore liable to be easily damaged. It must be absolutely gas-tight, for if it be leaky its buoyancy soon decreases. A mere pinhole involves a steady loss of gas; so that it has to be constructed of a very special material and with infinite care, which implies great expense. The actual cost of the gas, too, to fill the immense balloon is no mean item of expense, and it is bound to require frequent replenishing. Owing to the varying volume of the gas with changes of temperature, it is necessary to carry ballast or complicated means of regulating the altitude. This again involves increasing the capacity of the balloon. The housing and the handling of the machine when on the ground all add to the expense.

The inflammability of the gas is a constant source of danger, and, for war purposes, where it may be desirable to use firearms, it seems very unsuitable.

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construct.

The resistance of the air

to the propulsion of such a machine is very small, so that it should be capable of travelling infinitely faster for the

same propulsive power. Since the covering need not be gas-tight, it can be made of cheaper material, and where the balloon costs thousands of pounds, the flyer need not cost as many hundreds. The cost of the gas is done away with, and, requiring but little assistance, the working costs would be much smaller. Finally, from the military point of view, it is practically invulnerable to bullets, nor is it liable to catch fire.

We now come to another point, the most important of all. I have already said that in aerial navigation speed is everything. To successfully navigate the air it is essential to be able to go at a rate faster than that of any ordinary wind that may be encountered. As this often attains to twenty or thirty miles an hour, a machine incapable of overcoming such can never

Now

hope to be a practical success. airships have been made to achieve this, but, though they may still be improved upon to some extent, there does not seem to be much hope that they can ever greatly exceed such a speed. They might perhaps succeed in travelling forty miles an hour, but even then they would only be able to do their ten miles against a strong wind, which is not a very practicable rate. With the air-car it is different. It has been proved theoretically that the faster an aeroplane is driven the more economical it is. The pressure of the air evidently increases about in proportion to the square of the speed; that is to say, if an apparatus of given area, travelling at twenty miles an hour, develops a pressure under it of 500 lbs., then, if propelled at forty miles it should lift not only double the weight, but four times as much, or 2000 lbs. In order to get the machine to travel double the speed it may perhaps be necessary to increase the engine power fourfold, but let the original engine weigh 250 lbs. and we could still easily afford, if required, to put in an engine of four times the weight, and we should then be able to carry double the useful load as well.

I think the above arguments are so entirely in favor of the gasless machine as to put the balloon entirely out of the question. But is this a one-sided view? Let us see what Professor Newcomb has to say: "There are several drawbacks to every form of flyer, either of which seems fatal to its extensive use, and which, taken together, throw it out of the field of competition."

His first objection to a machine on the aeroplane principle is that, depending on its area for support, the larger the weight to be carried the larger must the horizontal surface be. Hence to make a machine to carry double the weight involves enlarging the surface

in proportion. But as the surface is spread horizontally it requires greatly additional weight of framework to bear the strain. Yes; but in the first place we do not here propose discussing the use of any machine very much bigger than those now in use, and, secondly, the surfaces need not necessarily be spread out in one plane; by arranging them one above another, a very large area of support can be got without adding much to the weight of construction. Then, again, I have just pointed out that by increasing speed we can increase the lift without adding to the area, and as speed is, for other reasons, so desirable, it is highly probable that efforts will be made to augment the speed and so carry greater loads for the samesized machine.

In nature we find that the area of the wings of insects and birds does not increase in at all the same ratio as their weight. Thus a gnat's wings have a surface corresponding to 49 square feet for 1 lb. of weight, a bee presents some 5 square feet, while a sparrow has under three, a pigeon 14, and a vulture only 4 of a square foot per pound. If this sort of proportion were carried on we should find that our large machines do not call for nearly the same relative area as the smaller ones.

The next asserted objection to the flyer whose support is due to its progress through the air is that it cannot stop to have its machinery repaired or adjusted. This is partially true, but it is a matter of degree. The engines could be stopped for a few seconds while the machine soars downwards. Then, when we get experienced in practical flight, it seems quite probable that we shall be able to take advantage of the wind currents and soar like the great birds. It might then be possible to remain for long periods on end sailing around without the as

sistance of any motor. But, besides all this, the stoppage of the engine is hardly likely to be of frequent occurrence in the future, when better forms of motor are obtainable. How often does a steamer or a locomotive have to stop to adjust the engine?

We now get to another drawback which is very real; but it applies equally to the propelled balloon. This is, that an aerial machine cannot be navigated for long out of sight of the ground. Once it rises into a cloud or becomes enveloped in fog, it is impossible to tell which way one is going. The aeronaut is then in the same position as the mariner at sea, but, exposed to rapid and varying currents of wind, he cannot rely on "dead reckoning." Fog must always be a hindrance to aerial navigation. Yet so it is, to a large extent, to marine navigation.

When Professor Newcomb comes to speak of the larger the ship the greater the power and speed, this can only apply to two airships on the same model; the remark cannot refer to the comparison between a bulky airship and a compact aeroplane. But even this statement is not quite a happy one. He says that "at the present moment the two largest ships afloat are also those of highest speed." He apparently forgets the dashing destroyers racing at thirty-five knots an hour, or the still smaller motor-boats and hydroplanes.

So much, then, for the arguments in favor of the airship as opposed to the gasless flyer.

We now come to the second and chief problem of the discussion, that is as to whether aerial navigation is likely in the near future to become of real importance; that is to say, whether an aerial machine is likely to be able "to compete with the steamship, the railway, or the mail-coach in the carriage of passengers or mails."

Having decided that a machine of the aeroplane type is preferable to a dirigible balloon, let us adopt, for the sake of argument, the notion of an apparatus very similar to that now used by the Wrights, but perhaps slightly larger, so as to carry three or four, and able to attain a greater speed, say fifty miles an hour. Let this be capable of travelling for several hours on end, of going up to say 1000 feet, and to negotiate all ordinary winds. Considering the enormous strides made within the last year or two, it seems not at all unreasonable to hope that we may have such a vessel within the next year or two.

The carriage of passengers and mails is one thing, but it is quite another matter to compare the airship to an express train, as Professor Newcomb does later on, and discuss the relative coal consumption, presuming it to carry the same burden. He shows that the main resistance which a train travelling at high speed has to encounter is that of the air, but he omits to point out that while the air resistance to a train is wholly one of retardation, in a well-designed flying-machine almost the whole effort is utilized in lift.

But it seems hardly necessary to discuss the question of utilizing an airship for the transport of heavy goods; no one, I think, looks upon that as a likely accomplishment for a long time to come.

The chief sentence of the whole of Professor Newcomb's article that I take exception to is this: "Any use that we can make of the air for the purpose of transportation, even when our machinery attains ideal perfection, will be uncertain, dangerous, expensive, and inefficient, as compared with transportation on the earth and ocean."

We will consider each of these points in turn.

Uncertain.-Fogs may delay traffic,

But both of

so may gales of wind. these affect shipping to a very large extent, if not trains, and as a rule would only occur during a few hours in a month. Though adverse winds may reduce the speed of travel, this is purely a question of the speed with which the machine can travel. If motor cars can now exceed 100 miles an hour along a road there seems every likelihood of air-cars being able in future to greatly exceed this. If capable of going 150 miles an hour, a gale blowing forty miles per hour would make no serious difficulty.

Dangerous.--It is very generally supposed that it is dangerous to travel through the air, this assumption probably being due to a large extent to the fact that several inventors in their crude appliances, and without experience, have come to grief. But with a perfected machine one can hardly imagine what can happen to upset it in mid-air. Barring collisions, which, on account of the greater space, should be much rarer than collisions at sea, and such accidents as the breaking of a shaft or catching fire, it is difficult to see what could happen." Then people often imagine the horror of falling after a mishap, through thousands of feet to the ground, forgetting that in all probability nine-tenths of the traffic will be conducted within twenty or thirty feet of the ground. So that the effects of an accident would not be much more serious than in other modes of travel.

Expensive.-Why? An air-car to carry two or three will certainly not cost as much as a motor car. Its upkeep will probably prove far less since there are no expensive tires to wear out, nor is there the same continual shaking and vibration. The speed and directness of the route from door to

2 The breaking of a propeller blade, such as occurred so unfortunately in Mr. Orville Wright's machine, is hardly likely to happen again.

door will certainly render flying an economical mode of transport.

For

Inefficient.-As a means of travel, the air-car promises to be the most delightful possible. Probably much faster than any other means of getting from place to place, and, as I have just said, very likely one of the cheapest. the transport of mails and light goods the same arguments apply. If Mr. Wright has already carried an extra weight of 240 lbs., there can be no question as to the possibility of carrying light loads. There appears to be no difficulty whatever in steering or in landing on any desired spot. Why, then, should it be deemed inefficient?

Considering all these facts, and that improvements are bound to follow, there seems to be every likelihood that, in future, travelling through the air will offer so many advantages that it will become a common means of getting from place to place. Then, by superseding other methods of transport, it will grow into a subject of great importance and create new and wide-spreading industries.

The employment of the aerial vessel as an instrument of war is probably the most important question at the present moment for our naval and military authorities to consider.

Professor Newcomb, in referring to this subject, begins by dismissing the flyer as "out of the question," and adds "the airship proper or enlarged balloon is the only agency to be feared." Yet he then points out how vulnerable such a vessel is, and how "a single yeoman could with his rifle disable a whole fleet of airships approaching within range of his station." It seems to me that this fact alone puts the airship out of the question, that is as a really practical, dependable, and important instrument of war. The flyer, on the other hand, presents a much more difficult target, and is comparatively invulnerable, since one or

two bullets are not likely to affect it in the least, and even shells may pass right through an aeroplane without bringing it down.

It is pointed out that a conflict between rival airships is likely to be short; both would probably soon be riddled by bullets and brought to earth. But this is not the case with gasless machines. They would hold a balloon at their mercy. The duel between such I will leave to the imagination.

There are two distinct methods of utilizing air-craft for war. First, that most usually discussed, is as a means of rising high into the air to obtain a wide view of the country round, to soar at an altitude above the range of projectiles, to float over towns and fortresses and drop bombs upon them. The extent to which damage can be done by dropping explosives from a height can at present be but a matter of speculation. It may prove to be serious, but it may be found, as Professor Newcomb points out, that the difficulties are so great that not very much is possible of accomplishment in this line. For such purposes the balloon may perhaps be considered almost the more suitable.

There is, however, the other method which seems to me that most likely to be of real use, at all events in the early days of aerial navigation, yet it is one that has seldom been referred to in writings or discussions on the subject. This is the use of a swiftly moving small machine skimming over the ground and seldom rising to any height except to clear such obstacles as trees and houses. Such a machine should prove invaluable in war. For reconnoitring it may be compared to the cavalry horse, but with the following advantages: it would be far speedier, could go across any country whatever, taking walls, rivers, and other obstacles "in its stride," it could probably carry two or three men, so that one

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