ena_] resulting
from bringing of a needle into contact with a piece of amber or resin
fricated on silke clothe. Ye flame putteth me in mind of sheet lightning
on a small--how very small--scale. But I shall in my epistles abjure
Philosophy whereof when I come down to Sakly I'll give you enou'. I
began to scrawl at 5 mins. from 9 of ye clk. and have in writing consmd.
10 mins. My Ld. Somerset is announced.

"Farewell, Gd. bless you and help yr sincere friend.

"ISAAC NEWTON.

"_To_ DR. LAW, Suffolk."

[19] Kepler's laws may be called respectively, the law of path, the law
of speed, and the relationship law. By the "mass" of a body is meant the
number of pounds or tons in it: the amount of matter it contains. The
idea is involved in the popular word "massive."

[20] The equation we have to verify is

4[pi]^2r^3
gR^2 = -----------,
T^2

with the data that _r_, the moon's distance, is 60 times R, the earth's
radius, which is 3,963 miles; while T, the time taken to complete the
moon's orbit, is 27 days, 13 hours, 18 minutes, 37 seconds. Hence,
suppose we calculate out _g_, the intensity of terrestrial gravity, from
the above equation, we get

4[pi]^2 39.92 x 216000 x 3963 miles
_g_ = ---------- x (60)^3R = -----------------------------
T (27 days, 13 hours, &c.)^2

= 32.57 feet-per-second per second,

which is not far wrong.

[21] The two motions may be roughly compounded into a single motion,
which for a few centuries may without much error be regarded as a
conical revolution about a different axis with a different period; and
Lieutenant-Colonel Drayson writes books emphasizing this simple fact,
under the impression that it is a discovery.

[22] Members of the Accademia dei Lyncei, the famous old scientific
Society established in the time of Cosmo de Medici--older than our own
Royal Society.

[23] Newton suspected that the moon really did so oscillate, and so it
may have done once; but any real or physical libration, if existing at
all, is now extremely minute.

[24] An interesting picture in the New Gallery this year (1891),
attempting to depict "Earth-rise in Moon-land," unfortunately errs in
several particulars. First of all, the earth does not "rise," but is
fixed relatively to each place on the moon; and two-fifths of the moon
never sees it. Next, the earth would not look like a map of the world
with a