oon started on her career of revolution round the earth, we
may well suppose that her orbit was much smaller than at present. She
was influenced by counteracting forces, those of gravitation drawing her
towards the centre of gravity of the earth,[1] and the centrifugal
force, which in the first instance was the stronger, so that her orbit
for a lengthened period gradually increased until the two forces, those
of attraction and repulsion, came into a condition of equilibrium, and
she now performs her revolution round the earth at a mean distance of
240,000 miles, in an orbit which is only very slightly elliptical.[2]
How the period of the moon's rotation is regulated by the earth's
attraction on her molten lava-sheets, first at the surface, and now
probably below the outer crust, has been graphically shown by Sir Robert
Ball,[3] but it cannot be doubted that once the moon was appreciably
nearer to our globe than at present. The attraction of her mass produced
tides in the ocean of correspondingly greater magnitude, and capable of
effecting results, both in eroding the surface and in transporting
masses of rock, far beyond the bounds of our every-day experience.

Of all the heavenly bodies, the sun excepted, the moon is the most
impressive and beautiful. As we catch her form, rising as a fair
crescent in the western sky after sunset, gradually increasing in size
and brilliancy night after night till from her circular disk she throws
a full flood of light on our world and then passes through her
decreasing phases, we recognise her as "the Governor of the night," or
in the words of our own poet, when in her crescent phase, "the Diadem of
night." Seen through a good binocular glass, her form gains in
rotundity; but under an ordinary telescope with a four-inch objective,
she appears like a globe of molten gold. Yet all this light is
derivative, and is only a small portion of that she receives from the
sun. That her surface is a mass of rigid matter destitute of any
inherent brilliancy, appears plain enough when we view a portion of her
disk through a very large telescope. It was the good fortune of the
author to have an opportunity for such a view through one of the largest
telescopes in the world. The 27-inch refractor manufactured by Sir
Howard Grubb of Dublin, for the Vienna observatory, a few years ago, was
turned on a portion of the moon's disk before being finally sent off to
its destination; and seen by the aid of such