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.  Some of the sun’s metals do not appear.  Stars differ in their very substance, and will, no doubt, introduce new elements to us unknown before.

The theory that all nebulae are very distant clusters of stars is utterly disproved by the clearest proof that some of them are only incandescent gases of one or two kinds.

Discoveries of New Bodies.—­Vulcan, the planet nearest the sun (page 138).  The two satellites of Mars were discovered by Mr. Hall, U. S. Naval Observatory, August 11th, 1877 (page 161).  “The outer one is called Diemas; the inner, Phobus.

Sir William Herschel thought he discovered six satellites of Uranus.  The existence of four of them has been disproved by the researches of men with larger telescopes.  Two new ones, however, were discovered by Mr. Lassell in 1846.

Saturn’s Rings are proved to be in a state of fluidity and contraction (page 171).

Meteors and Comets.—­The orbits of over one hundred swarms of meteoric bodies are fixed:  their relation to, and in some cases indentity with, comets determined.  Some comets are proved to be masses of great weight and solidity (page 133).