_G._ (_with growing interest_). "That sounds neater. You might work the chambers by electricity."
_I_. "We could even have an electric gun. Conceive a bobbin wound with insulated wire in lieu of thread, and having the usual hole through the axis of the frame. If a current of electricity be sent through the wire, the bobbin will become a hollow magnet or "solenoid," and a plug of soft iron placed at one end will be sucked into the hole. In this experiment we have the germ of a solenoid cannon. The bobbin stands for the gun-barrel, the plug for the bullet-car, and the magnetism for the ejecting force. We can arrange the wire and current so as to draw the plug or car right through the hole or barrel, and if we have a series of solenoids end to end in one straight line, we can switch the current through each in succession, and send the projectile with gathering velocity through the interior of them all. In practice the barrel would consist of a long straight tube, wide and strong enough to contain the bullet-car without flexure, and begirt with giant solenoids at intervals. Each of the solenoids would be excited by a powerful current, one after the other, so as to urge the projectile with accelerating speed along the tube, and launch it into the vast."
_G_. "That looks still better than the pneumatic gun."
_I_. "A magnetic gun would have several advantages. For instance, the currents can be sent through the solenoids in turn as quickly as we desire by means of a commutator in a convenient spot, for instance, at the b.u.t.t end of the gun, so as to follow up the bullet with ease, and give it a planetary flight. By a proper adjustment of the solenoids and currents, this could be done so gradually as to prevent a starting shock to the occupants of the car. The velocity attained by the car would, of course, depend on the number and power of the solenoids. If, for example, each solenoid communicated to the car a velocity of nine yards per second, a thousand solenoids, each magnetically stronger than another in going from breech to muzzle, would be required to give a final velocity of five miles a second. In such a case, the length of the barrel would be at least 1,000 yards. Economy and safety would determine the best proportions for the gun, but we are now considering the feasibility of the project, not its cost. With regard to position and supports, the gun might be constructed along the slope of a hill or mound steep enough to give it the angle or elevation due to the aim. As the barrel would not have to resist an explosive force, it should not be difficult to make, and the inside could be lubricated to diminish the friction of the projectile in pa.s.sing through it. Moreover, it is conceivable that the car need never touch the sides, for by a proper adjustment of the magnetism of the solenoids we might suspend it in mid-air like Mahomet"s coffin, and make it glide along the magnetic axis of the tube."
_G_. "It seems a promising idea for an actual gun, or an electric despatch and parcel post, or even a railway. The bullet, I suppose, would be of iron."
_I_. "Probably; but aluminium is magnetic in a lower degree than iron, and its greater lightness might prove in its favour. We might also magnetise the car, say by surrounding it with a coil of wire excited from an acc.u.mulator on board. The car, of course, would be hermetically sealed, but it would have doors and windows which could be opened at pleasure. In open s.p.a.ce it would be warmed and lighted by the sun, and in the shadow of a planet, if need were, by coal-gas and electricity.
In either case, to temper the extremes of heat or cold, the interior could be lined with a non-conductor. Liquefied oxygen or air for breathing, and condensed fare would sustain the inmates; and on the whole they might enjoy a comfortable pa.s.sage through the void, taking scientific observations, and talking over their experiences."
_G_. "It would be a novel observatory, quite free from atmospheric troubles. They might be able to make some astronomical discoveries."
_I_. "A novel laboratory as well, for in s.p.a.ce beyond the attraction of the earth there would be no gravity. The travellers would not feel a sense of weight, but as the change would be gradual they would get accustomed to it, and suffer no inconvenience."
_G_. "They would keep their gravity in losing it."
_I_. "The car, meeting with practically no resistance in the ether, would tend to move in the same direction with the same velocity, and anything put overboard would neither fall nor rise, but simply float alongside. When the car came within the sensible attraction of the moon, its velocity would gradually increase as they approached each other."
_G_. "Always supposing the aim of the gun to have been exact. You might hit the moon, with its large disc and comparatively short range, provided no wandering meteorite diverted the bullet from its course; but it would be impossible to hit a planet, such as Venus or Mars, a mere point of light, and thirty or forty million miles away, especially as both the earth and planet are in rapid motion. A flying rifle-shot from a lightning express at a distant swallow would have more chance of success. If you missed the mark, the projectile would wheel round the planet, and either become its satellite or return towards the earth like that of Jules Verne in his fascinating romance."
_I_. "Jules Verne, and other writers on this subject, appear to have a.s.sumed that all the initial effort should come from the cannon. Perhaps it did not suit his literary purpose to employ any other driving force.
At all events he possessed one in the rockets of Michel Ardan, the genial Frenchman of the party, which were intended to break the fall of the projectile on the moon."
_G_. "If I recollect, they were actually fired to give the car a fillip when it reached the dead-point on its way back to the earth."
_I_. "Even in a vacuum, where an ordinary propeller could not act, the bullet may become a prime mover, and co-operate with the gun. A rocket can burn without an atmosphere, and the recoil of the rushing fumes will impel the car onwards."
_G_. "Do you think a rocket would have sufficient power to be of any service?"
_I_. "Ten or twelve large rockets, capable of exerting a united back pressure of one and a half tons during five or six minutes on a car of that weight at the earth"s surface, would give it in free s.p.a.ce a velocity of two miles a second, which, of course, would not be lost by friction."
_G_. "So that it would not be absolutely necessary to give the projectile an initial velocity of five miles a second."
_I_. "No; and, besides, we are not solely dependent on the rocket. A jet of gas, at a very high pressure, escaping from an orifice into the vacuum or ether, would give us a very high propelling force. By compressing air, oxygen, or coal-gas (useful otherwise) in iron cylinders with closed vents, which could be opened, we should have a store of energy serviceable at any time to drive the car. In this way a pressure or thrust of several tons on the square inch might be applied to the car as long as we had gas to push it forwards."
_G_. "Certainly, and by applying the pressure, whether from the rocket or the gas, to the front and sides, as well as to the rear of the car, you would be able to regulate the speed, and direct the car wherever you wanted to go."
_I_. "Moreover, beyond the range of gravitation, we could steer and travel by pumping out the respired air, or occasionally projecting a pebble from the car through a stuffing box in the wall, or else by firing a shot from a pistol."
_G_. "You might even have a battery of machine guns on board, and decimate the hosts of heaven."
_I_. "Our bullets would fly straight enough, anyhow, and I suppose they would hit something in course of time."
_G_. "If they struck the earth they would be solemnly registered as falling stars."
_I_. "Certainly they would be burnt up in pa.s.sing through the atmosphere of a planet and do no harm to its inhabitants."
_G_. "Well, now, granting that you could propel the car, and that although your gun was badly aimed you could steer towards a planet, how long would the journey take?"
_I_. "The self-movement of the car would enable us to save time, which is a matter of the first importance on such a trip. In the plan of Jules Verne, the bullet derives all its motion from the initial effort, and consequently slows down as it rises against the earth"s attraction, until it begins again to quicken under the gravitation of the moon.
Hence his voyage to our satellite occupied four days. As we could maintain the velocity of the car, however, we should accomplish the distance in thirteen hours at a speed of five miles a second, and more or less in proportion."
_G_. "About as long as the journey from London to Aberdeen by rail. What about Mars or Venus?"
_I_. "At the same speed we should cover the 36,000,000 miles to these planets in 2,000 hours, or 84 days, that is, about three months. With a speed of ten miles a second, which is not impossible, we could reach them in six weeks."
_G_. "One could scarcely go round the world in the same time. But, having got to a planet, how are you going to land on it? Are you not afraid you will be dissipated like a meteorite by the intense heat of friction with the planet"s atmosphere, or else be smashed to atoms by the shock?"
_I_. "We might steer by the stars to a point on the planet"s...o...b..t, mathematically fixed in advance, and wait there until it comes up. The atmosphere of the approaching planet would act as a kind of buffer, and the fall of the car could be further checked by our means of recoil, and also by a large parachute. We should probably be able to descend quite slowly to the surface in this way without damage; but in case of peril, we could have small parachutes in readiness as life-buoys, and leap from the car when it was nearing the ground."
_G_. "I presume you are taking into account the velocity of the planet in its...o...b..t? That of the earth is 18 miles a second, or a hundred times faster than a rifle bullet; that of Venus, which is nearer the sun, is a few miles more; and that of Mars, which is further from the sun, is rather less."
_I_. "For that reason the more distant planets would be preferable to land on. Ura.n.u.s, for instance, has an orbital velocity of four miles a second, and his gravity is about three-fourths that of the earth.
Moreover, his axis lies almost exactly on the plane of the ecliptic, so that we could choose a waiting place on his...o...b..t where the line of his axis lay in the direction of his motion, and simply descend on one of his poles, at which the stationary atmosphere would not whirl the car, and where we might also profit by an ascending current of air. The attraction of the sun is so slight at the distance of Ura.n.u.s, that a stone flung out of the car would have no perceptible motion, as it would only fall towards the sun a mere fraction of an inch per second, or some 355 feet an hour; hence, as Dr. Preston has calculated, one ounce of matter ejected from the car towards the sun every five minutes, with a velocity of 880 feet a second, would suffice to keep a car of one and a half tons at rest on the orbit of the planet. Indeed, the vitiated air, escaping from the car through a small hole by its own pressure, would probably serve the purpose. Just before the planet came up, and in the nick of time we could fire some rockets, and give the car a velocity of two or three miles a second in the direction of the planet"s motion, so that he would overtake us, with a speed not over great to ensure a safe descent. Our parachutes would be out, and at the first contact with the atmosphere, the car would probably be blown away; but it would soon acquire the velocity of the planet, and gradually sink downwards to the surface."
_G_. "What puzzles me is how you are to get back to the earth."
_I_. "Whoever goes must take the risk; but if, as appears likely, both Mars and Venus are inhabited by intelligent beings, we should probably be able to construct another cannon and return the way we came."
_G_. (_smiling_). "Well, I confess the project does not look so impracticable as it did. After all, travelling in a vacuum seems rather pleasant. One of these days, I suppose, we astronomers will be packed in bullets and fired into the ether to observe eclipses and comets" tails."
_I_. "In all that has been said we have confined ourselves to ways and means already known; but science is young, and we shall probably discover new sources of energy. It may even be possible to dispense with the gun, and travel in a locomotive car. Lord Kelvin has shown that if Lessage"s hypothesis of gravitation be correct, a crystal or other body may be found which is lighter along one axis than another, and thus we may be able to draw an unlimited supply of power from gravity by simply changing the position of the crystal; for example, by raising it when lighter, and letting it fall when heavier. This form of "perpetual motion" might be equally obtainable if Dr. Preston"s[3] theory of an ether as the cause of gravity be true. Indeed, Professor Poynting is now engaged in searching for such a crystal, which, if discovered, will upset the second law of thermo-dynamics. I merely mention this to show that science is on the track of concealed motive powers derived from the ether, and we cannot now tell what the engines of the future will be like. For ought we know, the time is coming when there will be a regular mail service between the earth and Mars or Venus, cheap trips to Mercury, and exploring expeditions to Jupiter, Saturn, or Ura.n.u.s."
[Footnote 3: _Philosophical Magazine_, February, 1895.]
CHAPTER III.
A NEW FORCE.
"SIR,
"I have read your article on the possibility of travelling to the other members of the Solar system with much interest. It is a problem at which I, myself, have been working for a great many years, and I believe that I have now discovered a means of solving it in a practical manner. If you would care to see my experiments, and will do me the honour of coming here, I shall be glad to show them in confidence any time you may appoint.--Yours truly,
"NASMYTH CARMICHAEL."
The above letter, marked "Private," was forwarded to me through the editor of _The Day After To-morrow_. The writer of it was a total stranger to me, even by report, and at first I did not know what to make of it. Was the man a charlatan, or a "crank?" There were no signs of craziness or humbug in his frank and simple sentences. Had he really found out a way of crossing the celestial s.p.a.ces? In these days it is better not to be too sceptical as to what science will accomplish. It is, in fact, wise to keep the mind open and suspend the judgment. We are standing on the threshold of the Arcana, and at any hour the search-light of our intellect may penetrate the darkness, and reveal to our wondering gaze the depths of the inner mechanism of Nature.
I resolved to accept his invitation.
A few days later I presented myself at the home of my unknown correspondent. It was a lonely little cottage, in the midst of a wild flat or waste of common ground on the outskirts of London. I should say it had once been the dwelling of a woodman engaged in the neighbouring forest. A tall, thick hedge of holly surrounded the large garden, and almost concealed it from the curiosity of an occasional wanderer on the heath.
Certainly it did not look the sort of place to find a man of science, and the old misgivings a.s.sailed my mind in greater force than ever. Half regretting that I had come, and feeling in a dubious element, I opened the wicket, and knocked at the door.