"Regarding question four, 'At what precise moment will the moon present herself in the most favourable position, &c.?'
"Answer. – After what has been said above, it will be necessary, first of all, to choose the period when the moon will be in perigee, and also the moment when she will be crossing the zenith, which latter event will further diminish the entire distance by a length equal to the radius of the earth, i.e. 3919 miles; the result of which will be that the final passage remaining to be accomplished will be 214,976 miles. But although the moon passes her perigee every month, she does not reach the zenith always at exactly the same moment. She does not appear under these two conditions simultaneously, except at long intervals of time. It will be necessary, therefore, to wait for the moment when her passage in perigee shall coincide with that in the zenith. Now, by a fortunate circumstance, on the 4th December in the ensuing year the moon will present these two conditions. At midnight she will be in perigee, that is, at her shortest distance from the earth, and at the same moment she will be crossing the zenith.
"On the fifth question, 'At what point in the heavens ought the cannon to be aimed?'
"Answer. – The preceding remarks being admitted, the cannon ought to be pointed to the zenith of the place. Its fire, therefore, will be perpendicular to the plane of the horizon; and the projectile will soonest pass beyond the range of the terrestrial attraction. But, in order that the moon should reach the zenith of a given place, it is necessary that the place should not exceed in latitude the declination of the luminary; in other words, it must be comprised within the degrees 0° and 28° of lat. N. or S. In every other spot the fire must necessarily be oblique, which would seriously militate against the success of the experiment.
"As to the sixth question, 'What place will the moon occupy in the heavens at the moment of the projectile's departure?'
"Answer. – At the moment when the projectile shall be discharged into space, the moon, which travels daily forward 13° 10' 35", will be distant from the zenith point by four times that quantity, i.e. by 52° 42' 20", a space which corresponds to the path which she will describe during the entire journey of the projectile. But, inasmuch as it is equally necessary to take into account the deviation which the rotary motion of the earth will impart to the shot, and as the shot cannot reach the moon until after a deviation equal to 16 radii of the earth, which, calculated upon the moon's orbit, are equal to about eleven degrees, it becomes necessary to add these eleven degrees to those which express the retardation of the moon just mentioned: that is to say, in round numbers, about 64 degrees. Consequently, at the moment of firing the visual radius applied to the moon will describe, with the vertical line of the place, an angle of sixty-four degrees.
"These are our answers to the questions proposed to the Observatory of Cambridge by the members of the Gun Club: —
"To sum up, —
"1st. The cannon ought to be planted in a country situated between between 0° and 28° of N. or S. lat.
"2ndly. It ought to be pointed directly towards the zenith of the place.
"3rdly. The projectile ought to be propelled with an initial velocity of 12,000 yards per second.
"4thly. It ought to be discharged at 10hrs. 46m. 40sec. of the 1st December of the ensuing year.
"5thly. It will meet the moon four days after its discharge, precisely at midnight on the 4th December, at the moment of its transit across the zenith.
"The members of the Gun Club ought, therefore, without delay, to commence the works necessary for such an experiment, and to be prepared to set to work at the moment determined upon; for, if they should suffer this 4th December to go by, they will not find the moon again under the same conditions of perigee and of zenith until eighteen years and eleven days afterwards.
"The Staff of the Cambridge Observatory place themselves entirely at their disposal in respect of all questions of theoretical astronomy; and herewith add their congratulations to those of all the rest of America.
"For the Astronomical Staff,
"J. M. BELFAST,
"Director of the Observatory of Cambridge."
CHAPTER V.
THE ROMANCE OF THE MOON
An observer endued with an infinite range of vision, and placed in that unknown centre around which the entire world revolves, might have beheld myriads of atoms filling all space during the chaotic epoch of the universe. Little by little, as ages went on, a change took place; a general law of attraction manifested itself, to which the hitherto errant atoms became obedient: these atoms combined together chemically according to their affinities, formed themselves into molecules, and composed those nebulous masses with which the depths of the heavens are strewed.
These masses became immediately endued with a rotary motion around their own central point. This centre, formed of indefinite molecules, began to revolve round its own axis during its gradual condensation; then, following the immutable laws of mechanics, in proportion as its bulk diminished by condensation, its rotary motion became accelerated, and these two effects continuing, the result was the formation of one principal star, the centre of the nebulous mass.
By attentively watching, the observer would then have perceived the other molecules of the mass, following the example of this central star, become likewise condensed by gradually accelerated rotation, and gravitating round it in the shape of innumerable stars. Thus was formed the Nebulæ, of which astronomers have reckoned up nearly 5000.
Amongst these 5000 nebulæ there is one which has received the name of the Milky Way, and which contains eighteen millions of stars, each of which has become the centre of a solar world.
If the observer had then specially directed his attention to one of the more humble and less brilliant of these stellar bodies, a star of the fourth class, that which is arrogantly called the Sun, all the phenomena to which the formation of the Universe is to be ascribed would have been successively fulfilled before his eyes. In fact, he would have perceived this sun, as yet in the gaseous state, and composed of moving molecules, revolving round its axis in order to accomplish its work of concentration. This motion, faithful to the laws of mechanics, would have been accelerated with the diminution of its volume; and a moment would have arrived when the centrifugal force would have overpowered the centripetal, which causes the molecules all to tend towards the centre.
Another phenomenon would now have passed before the observer's eye, and the molecules situated on the plane of the equator escaping, like a stone from a sling of which the cord had suddenly snapped, would have formed around the sun sundry concentric rings resembling that of Saturn. In their turn, again, these rings of cosmical matter, excited by a rotary motion round the central mass, would have been broken up and decomposed into secondary nebulosities, that is to say, into planets. Similarly he would have observed these planets throw off one or more rings each, which became the origin of the secondary bodies which we call satellites.
Thus, then, advancing from atom to molecule, from molecule to nebulous mass, from that to a principal star, from star to sun, from sun to planet, and hence to satellite, we have the whole series of transformations undergone by the heavenly bodies during the first days of the world.
Now, of those attendant bodies which the sun maintains in their elliptical orbits by the great law of gravitation, some few in their turn possess satellites. Uranus has eight, Saturn eight, Jupiter four, Neptune possibly three, and the Earth one. This last, one of the least important of the entire solar system, we call the Moon; and it is she whom the daring genius of the Americans professed their intention of conquering.
The moon, by her comparative proximity, and the constantly varying appearances produced by her several phases, has always occupied a considerable share of the attention of the inhabitants of the earth.
From the time of Thales of Miletus, in the fifth century b. c., down to that of Copernicus in the fifteenth and Tycho Brahé in the sixteenth century a. d., observations have been from time to time carried on with more or less correctness, until in the present day