n between Sun and Earth._-Men always knew that the
earth received light from the sun. They subsequently discovered
that the earth was momentarily held by the power [Page 270] of
gravitation. But it is a recent discovery that the light is one of
the principal agents in chemical changes, in molecular grouping and
world-building, thus making all kinds of life possible (p. 30-36).
The close connection of the sun and the earth will be still farther
shown in the relation of sun-spots and auroras. One of the most
significant instances is related on page 19, when the earth felt the
fall of bolides upon the sun. Members of the body no more answer to
the heart than the planets do to the sun.

_Hydrogen Flames._--It has been demonstrated that the sun flames
200,000 miles high are hydrogen in a state of flaming incandescence
(page 85).

_Sun's Distance._--The former estimate, 95,513,794 miles, has been
reduced by nearly one-thirtieth. Lockyer has stated it as low as
89,895,000 miles, and Proctor, in "Encyclopaedia Britannica," at
91,430,000 miles, but discovered errors show that these estimates
are too small. Newcomb gives 92,400,000 as within 200,000 miles
of the correct distance. The data for a new determination of this
distance, obtained from the transit of Venus, December 8th, 1874,
have not yet been deciphered; a fact that shows the difficulty
and laboriousness of the work. Meanwhile it begins to be evident
that observations of the transit of Venus do not afford the best
basis for the most perfect determination of the sun's distance.

Since the earth's distance is our astronomical unit of measure, it
follows that all other distances will be changed, when expressed
in miles, by this ascertained change of the value of the standard.

_Oxygen in the Sun._--In 1877 Professor Draper announced the discovery
of oxygen lines in the spectrum of the sun. The discovery was doubted,
and the methods used were criticised by Lockyer and others, but
later and more delicate experiments substantiate Professor Draper's
claim to the discovery. The elements known to exist in the sun
are salt, iron, hydrogen, [Page 271] magnesium, barium, copper,
zinc, cromium, and nickel. Some elements in the sun are scarcely, if
at all, discoverable on the earth, and some on the earth not yet
discernible in the sun.

_Substance of Stars._--Aldebaran (_Frontispiece_) shows salt, magnesium,
hydrogen, calcium, iron, bismuth, tellurium, antimony, and mercury.
S