in the
morning emerging from the rays of the sun, his motion is direct and
rapid; it afterwards becomes slower, and he becomes stationary when at
an elongation of 137 deg. from the sun; then his motion becomes retrograde,
and its velocity increases until he is in opposition to the sun at 180 deg.;
at this time the retrograde motion is most rapid, and afterwards
diminishes until he is 137 deg. distant from the sun on the other side, when
Mars again becomes stationary; his motion then becomes direct, and
increases in velocity until it reaches a maximum, when the planet is
again in conjunction with the sun. The retrograde motion of this planet
lasts for 73 days: and its arc of retrogradation is 16 deg.."

[2] It is not so easy to plot the path of the sun among the stars by
direct observation, as it is to plot the path of a planet; because sun
and stars are not visible together. Hipparchus used the moon as an
intermediary; since sun and moon are visible together, and also moon and
stars.

[3] This is, however, by no means the whole of the matter. The motion is
not a simple circle nor has it a readily specifiable period. There are
several disturbing causes. All that is given here is a first rough
approximation.

[4] The proof is easy, and ought to occur in books on solid geometry. By
a "regular" solid is meant one with all its faces, edges, angles, &c.,
absolutely alike: it is of these perfectly symmetrical bodies that there
are only five. Crystalline forms are practically infinite in number.

[5] Best known to us by his Christian name, as so many others of that
time are known, _e.g._ Raphael Sanzio, Dante Alighieri, Michael Angelo
Buonarotti. The rule is not universal. Tasso and Ariosto are surnames.

[6] It would seem that the fact that all bodies of every material tend
to fall at the same rate is still not clearly known. Confusion is
introduced by the resistance of the air. But a little thought should
make it clear that the effect of the air is a mere disturbance, to be
eliminated as far as possible, since the atmosphere has nothing to do
with gravitation. The old fashioned "guinea and feather experiment"
illustrates that in a vacuum things entirely different in specific
gravity or surface drop at the same pace.

[7] Karl von Gebler (Galileo), p. 13.

[8] It is of course the "silver lining" of clouds that outside observers
see.

[9] L.U.K., _Life of Galileo_, p. 26.

[10] _Note added September, 1892._ News from