Daniel Kirkwood

“ Mars was the first planet to exhibit indications of an axial revolution. As early as 1636 Fontana, a Neapolitan astronomer, had an imperfect view of a spot on the planet's disk. He reobserved the same figure in 1638, and from the changes noticed in its position and aspect he inferred the probability of the planet's rotation. He seems, however, to have made no effort to determine its period. ”

“ The velocity with which some meteoric bodies have entered the atmosphere has been greater than that which would have been acquired by simply falling toward the sun from any distance, however great. On the theory of their sidereal origin, this excess of velocity has been dependent on the primitive force of expulsion. ”

“ We have seen that at each return to perihelion the meteoric cluster is extended over a greater arc of its orbit. Now, Tuttle's comet and the August meteors undoubtedly constituted a single cluster previous to their entering the solar domain. It is evident, however, from the annual return of the shower during the last 90 years, that the ring is at present nearly if not quite continuous. That the meteoric mass had completed many revolutions before the ninth century of our era is manifest from the frequent showers observed between the years 811 and 841. ”

“ Such bodies, however, in consequence of their nearness to the sun, could hardly be detected except in transiting the solar disk."
It is well known that the disturbing influence of the other planets causes an advance in the position of Mercury's perihelion. In a century this change amounts to 10′ 43,′′ which, according to Leverrier, is 38" more than can be accounted for by the influence of the known planets. This great astronomer inferred, therefore, that a planet, or possibly a zone of extremely small asteroids, must exist within the orbit of Mercury. ”

“ They are the seat of movements of which no terrestrial phenomenon can afford any idea; masses of matter, the volume of which is many hundred times greater than that of the earth, completely changing their position and form in the space of a few minutes. ”

“ Swift will not only stimulate astronomers to renewed search for the planet so fortunately detected, but must lead also to a more thorough examination of the space within Mercury's orbit. It is not improbable that the detection of Vulcan may be merely the first in a series of similar discoveries. [2] The solar disk will doubtless be closely watched about February 11th-17th, March 19th-27th, and October 1st-14th, as it has been claimed that at these epochs small round spots have been seen passing across the sun. ”

“ WHEN the coincidence between the orbits of the November meteors and the comet of 1866 was first clearly established a few years since, it was supposed by astronomers that the so-called Leonids formed a single cluster, diffused through an arc of such length as to require three or four years to make its perihelion passage. The meteoric period was shown by Professor Newton, of Yale College, and J. C. Adams, of Cambridge University, to be thirty-three and one fourth years. ”

“ The distance of Vulcan from the centre of the system, though still uncertain, is supposed to be about one-seventh that of the earth. If this estimate be nearly correct, the solar light and heat at its surface must be about fifty times greater than at the surface of the earth. ”

“ This indicates a velocity of about 200 miles per second at the lower elevation, and hence a considerably greater initial velocity. An equal force when the sun had but little more than twice its present diameter would have been sufficient to carry the projected matter beyond the orbit of Neptune. ”

“ Two white circular spots are observed in the polar regions, which increase during the winter, and decrease in the summer, of each hemisphere respectively, and which may, therefore, be regarded as polar snows. ”

“ It is sufficiently obvious that we have yet much to learn in regard to the constitution of the Leonid ring, and that future observations from the 13th to the 15th of November may probably result in important discoveries. ”

“ We must now refer to a very unpleasant incident in the history of this interesting discovery. This is nothing less than the charge, by an eminent astronomer, that the observations and measurements claimed by Dr. ”