_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 nebulæ 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). _Aerolites._-Some have a texture like our lowest strata of rocks. There is a geology of stars and meteors as well as of the earth. M. Meunier has just received the Lalande Medal from the Paris Academy for his treatise showing that, so far as our present knowledge can determine, some of these meteors once belonged to a globe developed in true geological epochs, and which has been separated into fragments by agencies with which we are not acquainted. [Illustration: Fig. 82.--Horizontal Pendulum.]