utwelling of lava from them which
has spread to a greater or less distance on either side. If the moon has
been fractured in this way, we can easily suppose that the craters formed
on these fissures, being in communication with the interior, might eject
some pulverulent white matter long after the rest of the surface with its
other types of craters had attained a quiescent stage.

The Tycho rays, when viewed under ordinary conditions, appear to extend
in unbroken bands to immense distances. One of the most remarkable,
strikes along the eastern side of Fracastorius, across the Mare Nectaris
to Guttemberg, while another, more central, extends, with local
variations in brightness, through Menelaus, over the Mare Serenitatis
nearly to the north-west limb. This is the ray that figures so
prominently in rude woodcuts of the moon, in which the Mare Serenitatis
traversed by it is made to resemble the Greek letter PHI. The Kepler,
Aristarchus, and Copernicus systems, though of much smaller extent, are
very noteworthy from the crossing and apparent interference of the rays;
while those near Byrgius, round Aristarchus, and the rays from Proclus,
are equally remarkable.

[Nichol found that the rays from Kepler cut through rays from Copernicus
and Aristarchus, while rays from the latter cut through rays from the
former. He therefore inferred that their relative ages stand in the
order,--Copernicus, Aristarchus, Kepler.]

As no branch of selenography has been more neglected than the observation
of these interesting but enigmatical features, one may hope that, in
spite of the exacting conditions as to situation and instrumental
requirements necessary for their successful scrutiny, the fairly equipped
amateur in this less favoured country will not be deterred from
attempting to clear up some of the doubts and difficulties which at
present exist as to their actual nature.

THE MOON'S ALBEDO, SURFACE BRIGHTNESS, &c.--Sir John Herschel maintained
that "the actual illumination of the lunar surface is not much superior
to that of weathered sandstone rock in full sunshine." "I have," he says,
"frequently compared the moon setting behind the grey perpendicular
facade of the Table Mountain, illuminated by the sun just risen in the
opposite quarter of the horizon, when it has been scarcely
distinguishable in brightness from the rock in contact with it. The sun
and moon being at nearly equal altitudes, and the atmosphere perfectly
free from