a N.W.
direction from Pentland.

SIMPELIUS.--Another grand circumvallation, almost as large as Pentland,
but unfortunately much foreshortened. One of its peaks on the E. rises to
a height of more than 12,000 feet above the floor, on which there is a
small central mountain. Between Simpelius and Pentland are several ring-
plains, most of which appear to have been squeezed and deformed into
abnormal shapes.

CURTIUS.--A magnificent formation, about 50 miles in diameter, with one
of the loftiest ramparts on the visible surface, rising at a mountain
mass on the N.E. to more than 22,000 feet, an altitude which is only
surpassed by peaks on the walls of Newton and Casatus. There is a bright
crater on the S.E. border and another on the W. The formation is too near
the S. limb for satisfactory scrutiny. Between Curtius and Zach is a fine
group of unnamed enclosures.

APPENDIX

DESCRIPTION OF THE MAP

The accompanying map, eighteen inches in diameter, represents the moon
under mean libration. Meridian lines and parallels of latitude are drawn
at every 10 deg., except in the case of the meridians of 80 deg. E. and
W. longitude, which are omitted to avoid confusion, and as being
practically needless. These lines will enable the observer, with the aid
of the Tables in the Appendix, to find the position of the terminator at
any time required. As astronomical telescopes exhibit objects inverted,
maps of the moon are always drawn upside down, and with the right and
left interchanged, as in the diagram above, which also shows how the
quadrants are numbered.

This circle [drawing of circle], intended to be .15708 in diameter,
represents a circle of one degree in diameter at the centre of the map,
and as the length of one selenographical degree is 18.871 miles, it
represents an area of nearly 280 square miles.

The catalogue is so arranged that, beginning with the W. limb, and
referring to the lists under the first and fourth, and the second and
third quadrants, all the formations falling within the meridians 90 deg.
to 60 deg., 60 deg. to 40 deg., 40 deg. to 20 deg., 20 deg. to 0 deg.
(the central meridian), and from 0 deg. to 20 deg., and so on, to the E.
limb, will be found in convenient proximity in the text.

In the Catalogue, N. S. E. W. are used as abbreviations for the cardinal
points.

LIST OF THE MARIA, OR GREY PLAINS, TERMED "SEAS," &c.

FIRST QUADRANT.

Mare Tranquilitatis (nearly the whole), page 5.