L.--Sometimes called "the railroad," is a remarkable and
almost unique formation on the W. side of Birt, extending for about 65
miles from N.E. to S.W. in a nearly straight line, terminating on the
south at a very peculiar mountain group, the shape of which has been
compared to a stag's horn, but which perhaps more closely resembles a
sword-handle,--the wall representing the blade. When examined under
suitable conditions, the latter is seen to be slightly curved, the S.
half bending to the west, and the remainder the opposite way. The
formation is not a ridge, but is clearly due to a sudden change in the
level of the surface, and thus has the outward characteristics of a
"fault" Along the upper edge of this gigantic cliff (which, though
measures differ, cannot be anywhere much less than 500 feet high) I have
seen at different times many small craterlets and mounds. Near its N. end
is a large crater, and on the W. is a row of hillocks, running at right
angles to the cliff. No observer should fail to examine the wall under a
setting sun when the nearly perpendicular E. face of the cliff is
brilliantly illuminated.

NICOLLET.--A conspicuous little ring-plain on the E. of Birt, and
somewhat smaller. Between the two is a still smaller crater, from near
which runs a low mountain range, nearly parallel to the straight wall, to
the region S.E. of the Stag's Horn Mountains. Here will be found three
small light-surrounded craters arranged in a triangle, with a somewhat
larger crater in the middle.

PURBACH.--An immense enclosure of irregular shape, approximating to that
of a rhomboid with slightly curved sides. It is fully 60 miles across,
and the walls in places exceed 8000 feet in altitude, and include many
depressions, large and small. On the E. inner slope are some fine
terraces and several craters. The continuity of the circumvallation is
broken on the N. by a great ring-plain, on the floor of which I have seen
a prominent cleft and a crater near the S. side. There is a large bright
crater in the interior of Purbach, S. of the centre, two others on the W.
half of the floor, and a few ridges.

REGIOMONTANUS.--A still more irregular walled-plain, of about the same
area, closely associated with the S. flank of Purbach, having a rampart
of a similar complex type, traversed by passes, longitudinal valleys, and
other depressions. Schmidt alone shows the especially fine example of a
crater-row, which is not a difficult object, in