heophilus. They resemble a consolidated stream of
"ropy" lava which has flowed through and over the wall and down the
_glacis_. The arrangement of the ridges within Cyrillus is very
noteworthy, as is also the triple mountain near the centre of the floor.
The fine curved cleft thereon traverses the W. side, sweeping round the
central mountains, and then turning to the south. I have only
occasionally seen it in its entirety. There are also two oblong dark
patches on the S. side of the interior. The S. wall of Cyrillus is broken
by a narrow pass opening out into a valley situated on the plateau which
bounds the W. side of the oblong formation lying between it and
Catherina, and overlooking a curious shallow square-shaped enclosure
abutting on the S.W. side of Cyrillus.

CATHERINA.--The largest of the three great formations: a ring-plain with
a very irregular outline, extending more than 70 miles in a meridional
direction, and of still greater width. The wall is comparatively narrow
and low on the N.E. (8000 feet above the floor), but on the N.W. it rises
to more than double this height, and is broken by some large depressions.
The inner slope on the S.E. is very gentle, and includes two bright
craters, but exhibits only slight indications of terraces. The most
remarkable features on an otherwise even interior are the large low
narrow ring (with a crater within it), occupying fully a third of the
area of the floor, and a large ring-plain on the S. side.

MADLER.--The interest attaching to this formation is not to be measured
by its size, for it is only about 20 miles in diameter, but by the
remarkable character of its surroundings. Its bright regular wall, rising
6000 feet on the E. and only about half as much on the W., above a rather
dark interior, is everywhere continuous, except at one place on the N.
Here there is a narrow gap (flanked on the E. by a somewhat obscure
little crater) through which a curious bent ridge coming up from the N.
passes, and, extending on to the floor, expands into something resembling
a central mountain. Under a high sun Madler has a very peculiar
appearance. The lofty E. wall is barely perceptible, while the much lower
W. border is conspicuously brilliant; and the E. half of the floor is
dark, while the remainder, with two objects representing the loftier
portions of the intrusive ridge, is prominently white. Under an evening
sun, with the terminator lying some distance to the W., a very rema