1875.| The Illuminated Disc of the Moon. 5 
45 east of the meridian, s the position of the sun 45° west 
of the meridian. 
Fic. 3. 
H 
Under the above conditions the straight line of the moon 
will be at right angles to that part of the curved line formed 
by the equino@tial, on which the moon at the time is located. 
Thus the moon will appear tilted sideways as it were, as 
shown in this diagram, and the line of light and darkness 
on the moon will not appear at right angles to the horizon. 
If we draw a line at right angles to the line of light and 
shade on the moon, and produce this line as a straight line 
past the meridian, H R, this line will not now pass through 
the sun’s centre, but will be traced in the direction of M Q, 
and will pass considerably above the sun. 
When the moon reaches the meridian, the sun, go’ from 
it, will be on the horizon and in the west. The moon will 
then appear in the position as regards the line of light and 
shade vertical, as shown in the following diagram (Fig. 4), 
BiGs4e 
Ss 
ik Jal 
where, as before, H M is a part of the meridian, EHS the 
horizon, M the moon, s the sun. A line drawn at right 
angles to the line of light and shade on the moon will now, 
if produced, be a line parallel to the horizon, and will not 
