1Nicetas of Syracuse (whose date I am not able to give) seems to have been aware of the diurnal movement of the earth round its axis.

2M. de l’Épinois has, since then, published a still more complete collection of the various documents he had obtained permission to inspect at Rome; but this work is, unfortunately, out of print.

3“Principium 7^m.—Sancta Sedes Apostolica cui divinitus commissa est custodia depositi, potestas pascendi universam Ecclesiam ad salutem animarum, potest sententias theologicas vel quatenus cum theologicis nectuntur proscribere ut sequendas vel proscribere ut non sequendas, non unice ex intentione definitiv sententi infallibiliter decidendi veritatem, sed etiam absque ilia ex necessitate et intentione vel simpliciter vel pro determinatis adjunctis prospiciendi securitati4 doctrinÆ CatholicÆ. In hujusmodi declarationibus licet non sit doctrinÆ veritas infallibilis, quia hanc decidendi ex hypothesi non est intentio; est tamen infallibilis securitas. Securitatem dico tum objectivam doctrinÆ declaratÆ [vel simplicitea vel pro talibus adjunctis], tum subjectivam quatenus omnibus tutum est eam amplecti, et tutum non est, nec absque violatione debitÆ submissionis erga magisterium divinitus constitutum fieri potest, ut eam amplecti recusent.

“Coroll. C. Falsum est, auctoritatem propter quam debeatur assensus intellectus, solam esse auctoritatem Dei revelantis seu EcclesiÆ vel Pontificis infallibiliter definientis; sunt enim gradus assensus religiosi multiplices. In prÆsenti distinguendus est assensus fidei proprie et immediate divinÆ propter auctoritatem Dei revelantis; assensus fidei quam supra diximus mediate divinam propter auctoritatem infallibilitur definientis doctrinam ut veram non tamen ut revelatam; assensus religiosus propter auctoritatem universalis providentiÆ ecclesiasticÆ in sensu declarato.”—De Divina Traditione et Scriptura, p. 116, et seq. Ed. 1870.

4“Non coincidere hÆc duo, infallibilem veritatem et securitatem, manifestum est vel ab eo, quod secus nulla doctrina probabilis aut probabilior posset dici sana et secura.”

5It happens, curiously enough, that the doctrine of the perfect immobility of the Sun, which so shocked the Qualifiers of the Inquisition, is simply discarded by modern astronomers. No one now holds that the Sun is the centre of the whole universe, or that he is immovable. It is generally supposed that he travels in space, though not round any known centre, and the Earth and Planets with him.

6“Dico, che quando ci fosse vera dimostratione che il Sole stia nel centro del mondo, e la terra nel 3 cielo, e che il Sole non circonda la terra, ma la terra circonda il Sole, allora bisogneria andar con molta consideratione in esplicare le Scritture che paiono contrarie, e piÙ sotto dire che non l’ intendiamo, che dira che sia falso quello che si dimostra. Ma io non crederÒ che ci sia tale dimostratione fin che non mi sia mostrata, etc.”—Extract from Cardinal Bellarmine’s Letter to F. Foscarini.

7A brief but interesting rÉsumÉ of the Aristotelian physics is given in Whewell’s “History of the Inductive Sciences,” a work to which I shall have occasion to refer more than once.

8It is said that a weight dropped from the top of a very high tower falls slightly to the east, because the velocity of the axial rotation is greater at the summit of the tower than at its foot, and the stone or ball dropped partakes of the motion of the highest part of the tower from which it falls; this is perfectly true in theory; and experiments, made not only from the summits of towers but also in mines, tend to confirm it.

9Simplicio having said that the cause why parts of the earth are carried downwards was gravity, Salviati answers: “Voi errate, Signor Simplicio, voi dovevate dire, che ciaschedun sa, ch’ ella si chiama gravitÀ; ma io non vi domando il nome, ma dell’ essenza della cosa: della quale essenza voi non sapete punto piÙ di quello, che voi sappiate dell’ essenza del movente le Stelle in giro; eccetuatone il nome, che a questa È stato posto, e fatto familiare, e domestico per la frequente esperienza, che mille volte il giorno noi ne veggiamo; ma non È, che realmente noi intentiamo piÙ, che principio, o che virtÙ sia quella, che muove la pietra in giÙ, di quel noi sappiamo chi la muova in sÙ, separata del proiciente; o chi muova la Luna in giro, eccettochÈ (come ho detto) il nome, che piÙ singolare e proprio gli abbiamo assegnato di gravitÀ; dovechÈ a quello con termine piÙ generico assegniamo virtÙ impressa, a quello diamo intelligenza o assistente, o informante; e a infiniti altri moti diamo loro per cagione la natura.”

10It is curious that the notion of the universe being shaped as a curve returning into itself has been started by some modern German philosophers, founders of what has been called “non-Euclidian geometry.” The investigations of astronomers, however, rather point to the conclusion that the stellar universe has no centre, no symmetrical figure, though speculations such as these must always be uncertain.

11To speak of the circumference of a circle of infinite radius as being identical with a straight line (though practically true enough) is not rigidly accurate. We should say that they approximate infinitely to one another, or in mathematical phraseology, they are equal to each other in the limit.

12It is not intended here to deny what some writers state—that the friction caused by the Earth’s rotation does in some degree act upon the tidal wave. It is remarkable, so far as can be ascertained from observations taken at some small island at a distance from any continent, that the tidal wave of the Ocean only rises, even at the spring, about five or six feet. The enormous rise of water at some places arises from the tidal wave being driven into estuaries, mouths of rivers, and other narrow channels.

13These are the author’s words, spoken by Salviati: “Tra tutti gli nomini grandi, che sopra tal mirabile effetto di natura hanno filosofato, piÙ mi maraviglio del Keplero, che di altri, il quale d’ingegno libero, e acuto, e che aveva in mano i moti attribuiti alla terra, abbia poi dato l’orecchio, e assenso a predominii della Luna sopra l’acqua, e a proprietÀ occulte, e simili fanciullezze.”

14It is not intended to imply that these two Schools of thought stand on anything like the same scientific level.

15The spots on the Sun were seen at about the same period of time by Fabricius and by Father Scheiner, a Jesuit, as already mentioned.

16I must not be understood as implying that even doctrinal decisions promulgated by the Roman Congregations in their own name are considered by theologians to be infallible; such character belonging only to decisions addressed by the Pope himself to the Church.

17A curious instance of popular unacquaintance with astronomy was afforded some months ago, when the planet Venus, which one would think was a well-known object to most people, was mistaken for “the Star of Bethlehem;” and this mistake was by no means confined to the ignorant, but was shared by persons of education.

The planet was at the time a brilliant “morning star;” and the effect on the eye is more striking in these circumstances than when it is seen, as is very commonly the case, in the evening, shortly after sunset. I suppose this would account in some measure for the delusion.

In clearer and finer skies than those of England, Venus is sometimes so brilliant in the early morning as to startle an unaccustomed observer.

18Dr. Ward makes a curious mistake in one point; he speaks in one of the articles of The Dublin Review (which he then edited) of Copernicanism as destroying the old ideas as to above and below; that is to say, for instance, your idea of ascending on high towards heaven was thereby nullified, and ascending from the surface of the earth meant going in any direction which the earth’s rotation might place above your head at any particular moment. But Dr. Ward, who was doubtless thinking of the very old and exploded notion that the earth was a flat surface, does not seem to have been aware that this objection applies in principle to the Ptolemaic system also; Ptolemy knew that the earth was spherical in its shape, and consequently that what would be above a person in the eastern parts of India, to take an example, would be widely different from that which would be so at the westernmost point of Africa. It may, however, be admitted that an additional cause for bewilderment was presented by the diurnal rotation of the Earth, since it then appeared that the same point in space above you at noon would be far away below you at midnight.

19Quoted from an article in the “Revue des Questions Historiques,” 1867, “GalilÉe, son ProcÈs, sa Condemnation, d’aprÈs des documents inÉdits,” by M. Henri de l’Épinois.

20Tycho BrahÉ discovered two out of the principal inequalities in the Moon’s motion—known to astronomers as the Variation and the Annual Equation; the third, which is the most obvious of all and is called the Evection, was discovered by Ptolemy.

21The figurative interpretation, however, in this instance is as old as St. Augustine, though his speculations lead him to a different conclusion from that of modern scientific men; namely, that of supposing the actual creation to be the work of one moment.

22It is, I think, Mr. Proctor who uses this argument in one of his works, to prove how very doubtful a thing is the existence of highly organised and rational beings on the other planets.

23It is quite possible, as Mr. Lockyer has recently argued, that many objects that appear to us as stars, are in reality nebulÆ in a more or less advanced stage of condensation.

24The relative distances could be computed geometrically, even before the absolute distances were known, and in fact were so; Kepler’s third law affords a simple rule for calculating them, but they were known even previously.

25I may, perhaps, be permitted to recall to the reader’s mind, in a note, one or two of the main objections urged by the anti-Copernicans. One of these was that it would leave the atmosphere behind, the true answer to which is that the atmosphere itself is attracted by the force of gravity to the earth, and is carried round by the rotation, as everything else is; this Galileo did not perfectly understand, as may be seen by his remarks, both in the second and the fourth day’s dialogue. Another was this—and it was put forward by no less a man than Tycho BrahÉ—a stone dropped from a high tower ought to fall to the westward of the tower, because the tower would be carried on to the east by the earth’s rotation, and the stone would not; this, however, being contrary to experience. The real fact is that the stone partakes of the rotatory movement as much as the tower does, the two forces of rotation and gravity being combined according to the second law of motion, while the stone is falling; this Galileo did know. Supposing a very high tower, the stone ought to fall slightly to the east, on account of the superior velocity of rotation at the top of the tower to that at the bottom. It is said this experiment has been successfully tried, as stated in note, page 55.

26There are other laws, besides that of the inverse square of the distance, which would cause a body to move in an ellipse, at least if the force acting on it were placed, not in the focus, but in the centre of the orbit. The question has been discussed with reference to some of the binary stars which appear to move round one another in ellipses. No doubt is thereby raised as to the prevalence of the law of the inverse square in our own solar system, where it has been verified by long and careful observation; the doubt (I think we may say a comparatively slight one) is whether the same law extends to the whole stellar universe, where, of course, accurate observation is impracticable.

27I do not think the truth of this is affected by any of the great modern discoveries; though that of the Conservation of Energy approaches more nearly than others to Universal Gravitation in its importance.