When the existence of aerolites as celestial bodies was first recognised, Laplace suggested that they had been ejected from volcanoes on the Moon. This theory, although supported by Olbers and other astronomers, was soon rejected. Next, it was suggested that they were ejected from the Sun, and Proctor believed them to come from the giant planets. A very detailed discussion of the subject is to be found in Ball’s ‘Story of the Heavens’ (1886), in which he expresses views in harmony with those of the Austrian physicist Tschermak. Ball demonstrated that the meteors which fall to the Earth cannot have come from any other planet, nor from the Sun. Accordingly, he concluded that they were originally ejected by the volcanoes of the Earth many ages ago, when they were active enough to throw up pieces of matter with a velocity great enough to carry them away from the Earth altogether. Such meteors would, however, intersect the terrestrial orbit at each revolution. The alternative theory to this, supported by Schiaparelli and Lockyer, is that the aerolites are merely larger members of the meteor-swarms, which have been deflected from their paths. The chief objection to this theory is the absence of connection between the meteoric showers and the falls of aerolites and bolides. Only on one occasion was a meteoric stone observed to fall during a shower. On November 27, 1885, during the shower of Andromedid meteors from Biela’s comet, a large bolide, weighing more than eight pounds, fell at Mazapil, in Mexico. This, however, was the only case hitherto observed; and it may have been merely a coincidence. CHAPTER IX. THE STARS. The most remarkable progress in astronomy during the past century has been in the department of sidereal science, or the study of the Suns of space, observed for their own sakes, and not merely for the purpose of determining the positions of the Sun and Moon, and to assist navigation. Thanks to Herschel, the nineteenth century witnessed the steady development of stellar astronomy, combined with many important discoveries and investigations.