Denning’s observations on meteors resulted, as early as 1877, in the discovery of so-called “stationary radiants.” The radiant-point of a long enduring shower usually exhibits an apparent motion, resulting from the combined orbital motions of the Earth and the meteors; but Denning found that in some cases the shower, though lasting for months, persistently exhibited the same radiant-point, implying that the motion of the Earth must be insignificant compared with that of the meteors, computed by Ranyard at 880 miles per second. The difficulty of admitting so great a velocity led the French astronomer, _François Felix Tisserand_ (1845-1896), to doubt the existence of these stationary radiants; but the fact of their existence cannot be doubted, although no really satisfactory explanation has been offered. Another type of meteors comprises the bodies termed respectively as bolides, uranoliths, and aerolites,—stones which fall to the Earth from the sky. In 1800 the French Academy declared the accounts of stones having fallen from the heavens to be absolutely untrue. Three years later an aerolite fell at Laigle, in the Department of Orne, on April 26, 1803, attended by a terrific explosion. In the words of Flammarion, “Numerous witnesses affirmed that some minutes after the appearance of a great bolide, moving from south-east to north-east, and which had been perceived at Alençon, Caen, and Falaise, a fearful explosion, followed by detonations like the report of cannon and the fire of musketry, proceeded from an isolated black cloud in a very clear sky. A great number of meteoric stones were then precipitated on the surface of the ground, where they were collected, still smoking, over an extent of country which measured no less than seven miles in length.” Some aerolites, instead of being shattered into fragments, have been observed to fall to the Earth intact, and bury themselves in the ground. Numerous instances have been observed during the last century, and masses of meteoric stones have been found in positions which clearly indicate that they must have fallen from the sky. Chemists have made analyses of the elements in these remarkable bodies, and have found them to contain iron, magnesium, silicon, oxygen, nickel, cobalt, tin, copper, &c. The spectrum of these aerolites, raised to incandescence, has been studied by Vogel and by the Swedish observer, _Bernhardt Hasselberg_ (born 1848), who detected the presence of hydrocarbons, which are also present in cometary spectra.