terrific convulsions, I must pronounce it as certain that they can not have any part in giving birth to the new stars which astonished Tycho Brahe and Kepler, or to those which have blazed forth in the heavens in our own times. Though the greater cosmical bodies might, as Dr. Croll supposes, be heated by collisions so intensely as to be capable of diffusing heat and light for many millions of years, they could not undergo the rapid decline of brilliancy which temporary stars exhibit. Lockyer takes similar grounds in speaking of Nova-Cygni. "We are driven," says he, "from the idea that these phenomena are produced by the incandescence of large masses of matter, for, if so produced, the running down of brilliancy would be exceedingly slow," A planetary wreck, incorporating with the sun in the manner I have described, would sweep through his external matter at the rate of about two hundred and eighty miles a second. The heat produced mechanically at the expense of this high velocity would not be so great in quantity as that which might be expected from Dr. Croll's solar encounters; but, being confined to a very limited zone, it would attain much greater intensity, be more effective for dissociation, and prove a more efficient means for giving nebulæ their existence and the peculiar character which they exhibit.
Since spectrum analysis has been brought to bear on the new stars, the doctrine of their meteoric origin has obtained more currency in astronomical circles. Though the incorporation of a remote world with a greater sphere around which it previously revolved has been suggested as the cause of such meteoric action, the idea has been somewhat unproductive, in consequence of the loose manner in which inquiries on the subject have been conducted, and the little care which has been taken for obtaining correct solutions for the problems of motion and stability involved in the questions at issue. The consequences of instability and dismemberment in small orbits have been generally overlooked. Recent developments, however, show some steps for correcting the early errors and oversights in this new field of investigation. In his recent work on "The Struggle for Existence in the Heavens," Du Prel (alluding to the ultimate doom of the earth near the center of our system) states that our world will end its career, not as one gigantic meteor, but as numberless meteoric fragments; and then the great shower of stones in the solar atmosphere will show the inhabitants of some very remote orb such a spectacle as was to be seen by terrestrial astronomers in the constellation of Corona on the 12th of May, 1866. A similar conclusion has been expressed frequently in my writings during the past twenty-five years, especially in my papers published in the reports of the British Association for 1857 and 1861, and in my communications in the "Philosophical Magazine" for 1858, 1861, and 1872.
The meteoric phenomena of distant space may be profitably studied in connection with those to be seen on a diminutive scale in our at-