g the short time that it can be seen" (Hind's
'Introduction to Astronomy'). There are few stars which are comparable
with Mercury in brilliancy, when seen under the same light.]

[Footnote 13: I may notice another error sometimes made. It is said that
the shadow of a satellite _appears_ elliptical when near the edge of the
disc. The shadow is _in reality_ elliptical when thus situated, but
_appears_ circular. A moment's consideration will show that this should
be so. The part of the disc concealed by a _satellite_ near the limb is
also elliptical, but of course appears round.]

[Footnote 14: From a paper by Mr. Breen, in the 'Popular Science
Review,' October, 1864.]

[Footnote 15: 'Intellectual Observer' for July, 1867, to which magazine
the reader is referred for full details of Mr. Howlett's method of
observation, and for illustrations of the appliances he made use of, and
of some of his results.]

[Footnote 16: As the sun does not attain such an altitude as 18 deg. during
two months in the year, it is well to notice that the true length of the
sun's apparent solar diameter is determinable even immediately after
sun-rise, if the line of graduation is made to coincide with the
_horizontal_ diameter of the picture on the screen--for refraction does
not affect the length of this diameter.]

[Footnote 17: The words "Left" and "Right" indicate which end of the
sun's ecliptical diameter is uppermost at the dates in upper or lower
row respectively.]

LONDON:

PRINTED BY W. CLOWES AND SONS, DUKE STREET, STAMFORD STREET, AND CHARING
CROSS.

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