The Stars.

Even the most ignorant of us know that the stars appear to be of different degrees of brightness or of magnitude. These magnitudes are purely optical, since the three elements that affect it, the star's distance, size and intrinsic brilliancy, are all, except in a few cases, unknown quantities. Hipparchus, in the second century before Christ, divided all the stars visible to the naked. eye into six classes, placing the brightest stars in the first and the faintest in the sixth magnitude. This classification remained unaltered until the middle of the 19th century, when Argelander and Heis1 of Germany reexamined the magnitudes of all the stars visible to the naked eye, and each of them published star maps, the Uranometria Nova and the Atlas. Celestis Novus, respectively.

The keen eye of Heis mapped the Milky Way in five degrees of luminosity. He is one of the founders of variable star astronomy, and it is also largely owing to his untiring energy in the observation of meteors, that Schiaparelli was enabled to show that the orbits of certain meteor swarms were identical with those of certain comets.

Following his master in the line of variable star observations, Father Hagen, formerly of the Georgetown College Observatory, and called in 1906 by Pius X to the directorship of the Vatican Observatory, published an Atlas Stellarum Variabilium, which became at once an indispensable requisite for this branch of astronomy.15

In regard to the spectra of the stars, we all know that Secchi's classification is adhered to even at the present day, and that his name can scarcely be omitted with propriety even from an elementary text-book.16

14Edward Heis, in Popular Astronomy, No. 136, June-July, 1906.

15 Review of Series VI, by J. A. Parkhurst in the Astronomical Journal, Vol. XXXI, No. 4, May, 1910.

18For the judgment of an expert consult Scheiner's Astrophysical Spectroscopy, translated by Edwin B. Frost, at present director of the Yerkes Observatory.

Theoretical Astronomy.

Copernicus, in his epoch-making work, "De Orbium Coelestium Revolutionibus," was the first to give us a true knowledge of our solar system and of the position and motions of the earth. While probably not a priest, Copernicus was certainly in holy orders, and was encouraged to publish his theories by Cardinals and Bishops, and actually dedicated his work to the reigning Pope Paul III, by whom it was valued highly. The great beauty and cogency of the Copernican system is its simplicity. He distinguished at the start between the real and apparent motions of the heavenly bodies, which had been hopelessly interwoven before. The earth's true eastward rotation on its axis explained the apparent westward rotation of the heavens. The motion of the earth about the sun like that of any other planet, explained in an elegant and correct manner the retrograde motions of the planets, which had been such perplexing difficulties before his

time.

There is not the least possibility of ever detecting any fallacy in the Copernican system, and of replacing it by another. Its truth is founded mainly, though not exclusively, on our knowledge of mechanics, a science of which the world was wholly ignorant until Galileo's experiments and reasonings gave us the laws of falling bodies, the pendulum, and, in fact, the whole of what we call mechanics, generally.

A direct proof of the earth's motion about the sun is furnished by the parallax of the stars, that is, their annual displacement on the celestial sphere in a small ellipse, which shows that the earth has really changed its position and moved to another point in its orbit. The aberration of light, which causes an apparent forward projection in a star's position, and the shifting of the spectral lines of the stars, prove conclusively that the earth is actually

in motion.

Newton's law of gravitation applies rigorously to all bodies whatsoever, not only to the sun and its planets, but also to the action of the planets among themselves. In consequence of this mutual attraction, the planets cannot move in such simple curves as are the conic sections, in which each one would move if it and

the sun alone existed. As these mutual attractions are very small when compared with the sun's overpowering influence, the discovery of the planet Neptune from the perturbation of Uranus "is justly reckoned as the greatest triumph of mathematical astronomy." 17 This glory is due to Leverrier, in France, in 1846, with whom Adams, in England, must also be associated, although his calculations were at first neglected. Leverrier happened to indicate the very spot within less than a degree where Neptune, the outermost planet of the solar system, nearly three thousand millions of miles away, was actually discovered.

And, finally, there are the works of Laplace, Leverrier, Tisserand and Poincaré, on celestial mechanics, which, amongst other things, investigate the mutual influence of the sun and its planets upon one another for all time to come. They show that, although all the elements of the planetary orbits are subject to change, those that concern our welfare on earth can vary only within imperceptible limits, while those that do not interest us have no limits set to their variations; in a word, that an overruling Providence has built the solar system on such a firm basis that, as far as its mechanism is concerned, it will endure forever in its present form.

Instrumental Inventions.

In regard to instrumental inventions, Clavius is credited with inventing the vernier, Scheiner was the first to construct an astronomical telescope, that is, one consisting of convex lenses exclusively, and to mount it equatorially. Boscovich was the first to use the ring micrometer. Braun designed the transit micrometer, which has latterly come into such extended use. He was also one of the first to suggest the principle on which the spectroheliograph is founded. Father Fargis, of Georgetown College, invented the photochronograph, which entirely eliminates the personal equation in time observations.18

17Young's General Astronomy, page 369.

18 Jesuit Astronomy in Popular Astronomy, No. 111, January, 1904, and No. 115, May, 1904.

The Symbol of the Earth.

As a minor matter, I would put in a plea for the restoration of the good old Catholic symbol for the earth. This is a circle with a cross on it, thus beautifully symbolizing the cross dominating the earth. An un-Catholic practice has put the cross inside the circle, and thus perverted its meaning, seeing in it only an allusion to the meridians and other circles generally drawn on the terrestrial globe.

Conclusion.

In this rapid survey of the work done by Catholics in astronomy the chief aim has been to present the subject in a popular form. While the names of many great men have been mentioned, the list is by no means exhausted. The work done by them was of necessity such as might be intelligible to the unprofessional reader, and hence, the technical astronomer may find much to reprehend in this sketch. All that we Catholics can, and do, lay claim to in speaking of our scientists, is that their names are justly illustrious and that they are amongst the greatest that the world has to show. We can establish their right to this distinction upon the most trustworthy testimony, generally non-Catholic. And we earnestly wish that the world at large, or at least its most fair-minded spokesmen, would, from the facts. presented, draw this one conclusion, that our holy Faith is at least not opposed to astronomy, a conclusion which, while falling far short of what we, as Catholics, would like to have drawn, may yet be the first and necessary step towards forming a correct judgment concerning the Catholic Church.

HISTORY SECTION

PROCEEDINGS

The Committee of the History Section of the College Department beg leave to report that the program as arranged was carried out, the sessions well attended, the papers of much merit, the discussions animated and thorough.

The Committee again urge that their sessions be held at 4 p. m. on both days.

The Committee for the following year will consist of the Rev. Francis J. Purtell, St. Charles Seminary, Philadelphia, chairman; the Rev. William J. Lallou, St. John's Church, Philadelphia, Pa.; the Rev. Joseph M. Woods, S. J., Woodstock College, Woodstock, Maryland.

JOHN J. O'HARA, S. J.,

Chairman.