star is soon freed from it and recovers its usual appearance. Nevertheless although these things be so, yet since both formerly in ancient times and likewise in our own age when it was a great sight and much talked of—a great change took place in the star of Venus both as to magnitude and colour, and even shape; and since a change which perpetually and constantly follows one particular star, and is seen to revolve along with it, must necessarily be set down as being in the star and not in the medium; and since through neglect of observation many things that are conspicuous in the heavens are passed by and lost to us; I think that this part of the ninth question is rightly admitted. The other part of the question is of the same kind; whether stars are in long revolutions of ages created and dissipated? There is a greater number of phenomena indeed to challenge this question than that about their augmentations and diminutions; but yet only of one kind. For as to the old stars, neither have we in all the memory of ages any record of the first birth of any of them (except the stories which the Arcadians of old told about the moon), nor is one of them missing. Of those however which have been regarded as comets, yet having the form and motion of stars, and being exactly like new stars, we have witnessed both appearances (of which we have likewise heard from the ancients) and disappearances; when they looked to some persons as if consumed, to some as if taken up (that is, as if having come down to us in their perigees, they returned again to the higher regions), to others as if rarefying and dissolving into ether. But all this question concerning new stars I refer to that place where I shall speak of comets. There remains another question, namely concerning the milky way; is the milky way a collection of small stars, or a continuous body, and part of the ether, of a middle nature between the ethereal and the starry? For that opinion concerning exhalations has itself long ago exhaled, not without censure of the wit of Aristotle, who ventured to invent such a matter', ascribing to a thing so constant and fixed a nature transitory and variable. And this question moreover, as I put it, seems on the point of being settled, if we believe the report of Galileo, who has resolved this confused appearance of light into stars numbered and placed. For the fact that the milky way Arist. Meteor. i. 8. does not hide from view those stars which are found within it, certainly does not settle the question, nor incline the balance either way. Only perhaps it proves by way of negation that the milky way is not situated below the starry heaven. For if it were, and if withal that continuous body of the milky way had any depth, our view would probably be intercepted. But if be situated at the same altitude as the stars which are seen through it, why may not stars be scattered in the milky way itself, as well as in the rest of the ether? This question therefore I admit likewise. And these six questions pertain to the substance of the heavenly bodies; namely, what is the substance of the heaven in kind, what that of the interstellar ether, what that of the milky way, and what that of the stars themselves, compared either with one another, or with our fire, or with their own body. As to the number, magnitude, configuration, and distance of the stars, besides the phenomena themselves and historical questions, of which I shall speak afterwards, the philosophical problems are mostly simple. With regard to the number there follows this other question; is the number of the stars that which appears, and which has been observed and set down by the diligence of Hipparchus, and included in his model of the celestial globe? For not only is that a poor reason that is given for the countless multitude of hidden stars not distinctly visible, which is usually seen in clear nights, especially during the winter; namely that these appearances are not smaller stars, but only radiations and flashings and as it were darts cast from the known stars; but the census now made by Galileo of the celestial population contains additional heads, not only in that cluster denominated the milky way, but likewise among the very stations and ranks of the planets. And stars become invisible, either by reason of smallness of body, or by reason of opacity (for I do not much approve of the term "tenuity," seeing that pure flame is a body of extreme tenuity), or by reason of elongation and distance. As for the question respecting the increase of the number of the stars by the generation of new ones, I refer it as before to the place where I shall speak of comets. Now with regard to the magnitude of the stars, the apparent magnitude belongs to phenomena, but the true magnitude to philosophical inquiry, within the limits of that twelfth problem; what is the true magnitude of each star, either measured, or at least compared? for it is easier so many to discover and prove that the globe of the moon is smaller than the globe of the earth, than that the globe of the moon is miles in circumference. We must therefore find exact magnitudes, if we can; and if they cannot be had, we must make use of comparative. Now true magnitudes are taken and concluded either by eclipses and shadows; or by extensions as well of light as of other virtues which each body shoots out and diffuses to a greater or less distance in proportion to its magnitude; or lastly by the symmetry of the universe, which by a kind of necessity governs and defines the portions of connatural bodies. We are not however to be bound by the statements of astronomers regarding the true magnitudes of stars; statements made (though it may seem a matter of great accuracy and subtlety) loosely and carelessly enough; but we must seek proofs (if there be any) more trustworthy and genuine. Now the magnitude and the distance of the stars mutually indicate each other from optical calculations; which themselves however require sifting. This question then concerning the true magnitude of the stars is the twelfth in number. Next comes another concerning their figure; whether the stars are globes; that is collections of matter in a solid round figure? To appearance there seem to be three figures of heavenly bodies; globular and beamy like the sun, globular and angular like the stars (the beams and angles referring only to sight, the globular form only to substance); globular simply, like the moon. For there is no star to be seen which is oblong or triangular or square, or of any other figure. And it seems natural that the greater masses of things should for their preservation and more perfect union collect into globes. The fourteenth question relates to distance; what is the true distance of any star in the depth of heaven? For the distances of the planets both from one another and from the fixed stars, laterally, or in the superficial compass of the heaven, are governed by their motions. But as I said before concerning the magnitude of the stars, that if an exact and measured magnitude is not to be had, we must take a comparative magnitude; so I say with respect to their distances; namely that if the distance (say from the earth to Saturn or Jupiter) cannot be exactly taken, yet let us make it certain that Saturn is higher than Jupiter. For neither is the interior system of the heaven, I mean the order of the planets in point of altitude, entirely 544 TRANSLATION OF THE "DESCR. GLOB. INTELL.” without controversy; nor were the doctrines now prevalent believed in former times. And even now the question whether Mercury or Venus be the higher, is still pending. Now distances are discovered either from parallaxes, or eclipses, or calculations of motions, or differences in apparent magnitude. And other aids are to be provided for the determination of this, which may be devised by human industry. The thicknesses or depths of the spheres also have relation to distances. |