CHAP. 8. (11.)—OF THE MAGNITUDE OF THE STARS.
This kind of reasoning carries the human mind to the heavens, and by contemplating the world as it were from thence, it discloses to us the magnitude of the three greatest bodies in nature[178]. For the sun could not be entirely concealed from the earth, by the intervention of the moon, if the earth were greater than the moon[179]. And the vast size of the third body, the sun, is manifest from that of the other two, so that it is not necessary to scrutinize its size, by arguing from its visible appearance, or from any conjectures of the mind; it must be immense, because the shadows of rows of trees, extending for any number of miles, are disposed in right lines[180], as if the sun were in the middle of space. Also, because, at the equinox, he is vertical to all the inhabitants of the southern districts at the same time[181]; also, because the shadows of all the people who live on this side of the tropic fall, at noon, towards the north, and, at sunrise, point to the west. But this could not be the case unless the sun were much greater than the earth; nor, unless it much exceeded Mount Ida in breadth, could he be seen when he rises, passing considerably beyond it to the right and to the left, especially, considering that it is separated by so great an interval[182].
The eclipse of the moon affords an undoubted argument of the sun’s magnitude, as it also does of the small size of the earth[183]. For there are shadows of three figures, and it is evident, that if the body which produces the shadow be equal to the light, then it will be thrown off in the form of a pillar, and have no termination. If the body be greater than the light, the shadow will be in the form of an inverted cone[184] the bottom being the narrowest part, and being, at the same time, of an infinite length. If the body be less than the light, then we shall have the figure of a pyramid[185], terminating in a point. Now of this last kind is the shadow which produces the eclipse of the moon, and this is so manifest that there can be no doubt remaining, that the earth is exceeded in magnitude by the sun, a circumstance which is indeed indicated by the silent declaration of nature herself. For why does he recede from us at the winter half of the year[186]? That by the darkness of the nights the earth may be refreshed, which otherwise would be burned up, as indeed it is in certain parts; so great is his size.
CHAP. 9. (12.)—AN ACCOUNT OF THE OBSERVATIONS THAT HAVE BEEN MADE ON THE HEAVENS BY DIFFERENT INDIVIDUALS.
The first among the Romans, who explained to the people at large the cause of the two kinds of eclipses, was Sulpicius Gallus, who was consul along with Marcellus; and when he was only a military tribune he relieved the army from great anxiety the day before king Perseus was conquered by Paulus[187]; for he was brought by the general into a public assembly, in order to predict the eclipse, of which he afterwards gave an account in a separate treatise. Among the Greeks, Thales the Milesian first investigated the subject, in the fourth year of the forty-eighth olympiad, predicting the eclipse of the sun which took place in the reign of Alyattes, in the 170th year of the City[188]. After them Hipparchus calculated the course of both these stars for the term of 600 years[189], including the months, days, and hours, the situation of the different places and the aspects adapted to each of them; all this has been confirmed by experience, and could only be acquired by partaking, as it were, in the councils of nature. These were indeed great men, superior to ordinary mortals, who having discovered the laws of these divine bodies, relieved the miserable mind of man from the fear which he had of eclipses, as foretelling some dreadful events or the destruction of the stars. This alarm is freely acknowledged in the sublime strains of Stesichorus and Pindar, as being produced by an eclipse of the sun[190]. And with respect to the eclipse of the moon, mortals impute it to witchcraft, and therefore endeavour to aid her by producing discordant sounds. In consequence of this kind of terror it was that Nicias, the general of the Athenians, being ignorant of the cause, was afraid to lead out the fleet, and brought great distress on his troops[191]. Hail to your genius, ye interpreters of heaven! ye who comprehend the nature of things, and who have discovered a mode of reasoning by which ye have conquered both gods and men[192]! For who is there, in observing these things and seeing the labours[193] which the stars are compelled to undergo (since we have chosen to apply this term to them), that would not cheerfully submit to his fate, as one born to die? I shall now, in a brief and summary manner, touch on those points in which we are agreed, giving the reasons where it is necessary to do so; for this is not a work of profound argument, nor is it less wonderful to be able to suggest a probable cause for everything, than to give a complete account of a few of them only.
CHAP. 10. (13.)—ON THE RECURRENCE OF THE ECLIPSES OF THE SUN AND THE MOON.
It is ascertained that the eclipses complete their whole revolution in the space of 223 months[194], that the eclipse of the sun takes place only at the conclusion or the commencement of a lunation, which is termed conjunction[195], while an eclipse of the moon takes place only when she is at the full, and is always a little farther advanced than the preceding eclipse[196]. Now there are eclipses of both these stars in every year, which take place below the earth, at stated days and hours; and when they are above it[197] they are not always visible, sometimes on account of the clouds, but more frequently, from the globe of the earth being opposed to the vault of the heavens[198]. It was discovered two hundred years ago, by the sagacity of Hipparchus, that the moon is sometimes eclipsed after an interval of five months, and the sun after an interval of seven[199]; also, that he becomes invisible, while above the horizon, twice in every thirty days, but that this is seen in different places at different times. But the most wonderful circumstance is, that while it is admitted that the moon is darkened by the shadow of the earth, this occurs at one time on its western, and at another time on its eastern side. And farther, that although, after the rising of the sun, that darkening shadow ought to be below the earth, yet it has once happened, that the moon has been eclipsed in the west, while both the luminaries have been above the horizon[200]. And as to their both being invisible in the space of fifteen days, this very thing happened while the Vespasians were emperors, the father being consul for the third time, and the son for the second[201].
CHAP. 11. (14.)—OF THE MOTION OF THE MOON.
It is certain that the moon, having her horns always turned from the sun, when she is waxing, looks towards the east; when she is waning, towards the west. Also, that, from the second day after the change, she adds 471⁄2 minutes[202] each day, until she is full, and again decreases at the same rate, and that she always becomes invisible when she is within 14 degrees of the sun. This is an argument of the greater size of the planets than of the moon, since these emerge when they are at the distance of 7 degrees only[203]. But their altitude causes them to appear much smaller, as we observe that, during the day, the brightness of the sun prevents those bodies from being seen which are fixed in the firmament, although they shine then as well as in the night: that this is the case is proved by eclipses, and by descending into very deep wells.