Part 10

I shall next produce the eye-witnesse of Galilæus, on which I most of all depend for the proofe of this Proposition, when he beheld the new Moone through his perspective, it appeared to him under a rugged and spotted figure, seeming to have the darker and enlightned parts divided by a tortuous line, having some parcels of light at a good distance from the other, and this difference is so remarkable, that you may easily perceive it through one of those ordinary perspectives, which are commonly sold amongst us, but for your better apprehending of what I deliver, I will set downe the Figure as I find it in Galilæus:

Suppose ABCD to represent the appearance of the Moones body being in a sextile, you may see some brighter parts separated at a pretty distance from the other, which can bee nothing else but a reflexion of the Sunne-beames upon some parts that are higher then the rest, and those obscure gibbosities which stand out towards the enlightened parts must bee such hollow and deepe places whereto the rayes cannot reach, but when the Moone is got further off from the Sunne, and come to that fulnesse, as this line BD doth represent her under, then doe these parts also receive an equall light, excepting onely that difference which doth appeare betwixt their sea and land. And if you do consider how any rugged body would appeare, being enlightned, you would easily conceive that it must necessarily seeme under some such gibbous unequall forme, as the Moone is here represented. Now for the infallibility of these appearances, I shall referre the reader to that which hath beene said in the 6th Proposition.

But Cæsar la Galla affirmes, that all these appearances may consist with a plaine superficies, if wee suppose the parts of the body to be some of them, Diaphanous, and some opacous; and if you object that the light which is conveyed to any diaphanous part in a plaine superficies must be by a continued line, whereas here there appeare many brighter parts among the obscure at some distance from the rest. To this he answers, it may arise from some secret conveyances and channels within her body, that doe consist of a more diaphanous matter which being covered over with an opacious superficies, the light passing through them may breake out a great way off, whereas the other parts betwixt may still remaine darke. Just as the River Arethusa in Sicile which runnes under ground for a great way, and afterwards breakes out againe. But because this is one of the chiefest fancies whereby hee thinkes hee hath fully answered the arguments of this opinion, I will therefore set downe his answere in his owne words, lest the Reader might suspect more in them then I have expressed.

Non est impossibile coecos ductus diaphani & perspicui corporis, sed opacâ superficie protendi, usque in diaphanam aliquam ex profundo in superficiem, emergentem partem, per quos ductus lumen longo postmodum interstitio erumpat, &c.

But I reply, if the superficies betwixt these two enlightened parts remaine darke because of its opacity, then would it alwaies be darke, and the Sunne could not make it partake of light more then it could of perspicuity: But this contradicts all experience as you may see in Galilæus, who affirmes that when the Sunne comes nearer to his opposition, then that which is betwixt them, both is enlightned as well as either. Nay this opposes his owne eye-witnesse, for he confesses himselfe that he saw this by the glasse. He had said before that he came to see those strange sights discovered by Galilæus his glasse with an intent of contradiction, and you may reade that confirmed in the weakenesse of this answere, which rather bewrayes an obstinate then a perswaded will, for otherwise sure hee would never have undertooke to have destroyed such certaine proofes with so groundlesse a fancy.

But it may bee objected, that 'tis almost impossible, and altogether unlikely that in the Moone thete should be any mountaines so high as those observations make them, for doe but suppose according to the common principles, that the Moones diameter unto the Earths is very neere to the proportion of 2. to 7, suppose withall that the Earths diameter containes about 7000 Italian miles, and the Moones 2000 (as is commonly granted) now Galiæus hath observed that some parts have been enlightened when they were the twentieth part of the diameter distant from the common terme of illumination, so that hence it must necessarily follow that there may bee some Mountaines in the Moone so high, that they are able to cast a shadow a 100 miles off. An opinion that sounds like a prodigie or a fiction; wherefore 'tis likely that either those appearances are caused by somewhat else besides mountaines, or else those are fallible observations, from whence may follow such improbable inconceiveable consequences.

But to this I answere:

1. You must consider the height of the Mountaines is but very little, if you compare them to the length of their shadowes. Sr. Walter Rawleigh observes that the Mount Athos now called Lacas casts its shadow 300 furlongs, which is above 37 miles, and yet that Mount is none of the highest, nay Solinus (whom I should rather believe in this kinde) affirmes that this Mountaine gives his shadow quite over the Sea, from Macedon to the Ile of Lemnos which is 700 furlongs or 84 miles, and yet according to the common reckoning it doth scarce reach 4 miles upwards, in its perpendicular height.

2. I affirme that there are very high Mountaines in the Moone. Keplar and Galilæus thinke that they are higher than any which are upon our earth. But I am not of their opinion in this, because I suppose they goe upon a false ground whilst they conceive that the highest mountaine upon the earth is not above a mile perpendicular.

Whereas 'tis the common opinion and found true enough by observation, that Olympus, Atlas, Taurus and Enius, with many others are much above this height. Tenariffa in the Canary Ilands is proved by computation to bee above 8 miles perpendicular, and about this height is the mount Perjacaca in America. Sr. Walter Rawleigh seemes to thinke, that the highest of these is neere 30 miles upright: nay Aristotle speaking of Caucasus in Asia, affirmes it to bee visible for 560 miles, as some interpreters finde by computation, from which it will follow, that it was 78 miles perpendicularly high, as you may see confirmed by Jacobus Mazonius, and out of him in Blancanus the Jesuite. But this deviates from the truth more in excesse then the other doth in defect. However though these in the moone are not so high as some amongst us, yet certaine it is they are of a great height, and some of them at the least foure miles perpendicular. This I shall prove from the observation of Galilæus, whose glasse can shew this truth to the senses, a proofe beyond exception and certaine that man must needs be of a most timerous faith who dares not believe his owne eye.

By that perspective you may plainely discerne some enlightned parts (which are the mountaines) to be distant from the other about the twentieth part of the diameter. From whence it will follow, that those mountaines must necessarily be at the least foure Italian miles in height.

For let BDEF be the body of the moone, ABC will be a ray or beame of the Sunne, which enlightens a mountaine at A and B is the point of contingency, the distance betwixt A and B must bee supposed to be the twentieth part of the diameter which is an 100 miles, for so far are some enlightened parts severed from the common terme of illumination. Now the aggregate of the quadrate from A B a hundred, and B G a 1000 will bee 1010000, unto which the quadrate arising from A G must be equall according to the 47th proposition in the first booke of elements. Therefore the whole line A G is somewhat more than 104, and the distance betwixt H A must be above 4 miles, which was the thing to be proved.

But it may be againe objected, if there be such rugged parts, and so high mountaines, why then cannot wee discerne them at this distance, why doth the moone appeare unto us so exactly round, and not rather as a wheele with teeth?

I answere, by reason of too great a distance, for if the whole body appeare to our eye so little, then those parts which beare so small a proportion to the whole will not at all be sensible.

But it may be replied, if there were any such remarkeable hils, why does not the limbe of the moone appeare like a wheele with teeth to those who looke upon it through the great perspective on whose witnesse you so much depend? or what reason is there that she appeares as exactly round through it as shee doth to the bare eye? certainely then either there is no such thing as you imagine, or else the glasse failes much in this discovery.

To this I shall answere out of Galilæus.

1. You must know that there is not meerely one ranke of mountaines about the edge of the moone, but divers orders, one mountaine behind another, and so there is somewhat to hinder those void spaces which otherwise, perhaps, might appeare.

Now where there be many hils, the ground seemes even to a man that can see the tops of all. Thus when the sea rages, and many vast waves are lifted up, yet all may appeare plaine enough to one that stands at the shore. So where there are so many hils, the inequality will be lesse remarkable, if it be discerned at a distance.

2. Though there be mountains in that part which appeares unto us, to be the limbe of the Moone, as well as in any other place, yet the bright vapours hide their appearance: for there is an orbe of thicke vaporous aire that doth immediatly compasse the body of the Moone, which though it have not so great opacity, as to terminate the sight, yet being once enlightened by the Sunne, it doth represent the body of the Moone under a greater forme, and hinders our sight from a distinct view of her true circumference. But of this in the next Chapter.

I have now sufficiently proved, that there are hills in the Moone, and hence it may seeme likely that there is also a world, for since providence hath some speciall end in all its workes, certainly then these mountaines were not produced in vaine, and what more probable meaning can wee conceive there should be, than to make that place convenient for habitation.

Proposition 10.

That there is an Atmo-sphæra, or an orbe of grosse vaporous aire, immediately encompassing the body of the Moone.

As that part of our aire which is neerest to the earth, is of a thicker substance than the other, by reason tis alwaies mixed with some vapours, which are continually exhaled into it. So is it equally requisite, that if there be a world in the Moone, that the aire about that should be alike qualified with ours. Now, that there is such an orbe of grosse aire, was first of all (for ought I can reade) observed by Meslin, afterwards assented unto by Keplar and Galilæus, and since by Baptistae Cisatus, Sheiner with others, all of them confirming it by the same arguments which I shall onely cite, and then leave this Proposition.

1. 'Tis observed, that so much of the Moone as is enlightened, is alwaies part of a bigger circle then that which is darker. Their frequent experience hath proved this, and an easie observation may quickely confirme it. But now this cannot proceede from any other cause so probable, as from this orbe of aire, especially when we consider how that planet shining with a borrowed light, doth not send forth any such rayes as may make her appearance bigger then her body.

2. 'Tis observed in the Solary eclipses, that there is a great trepidation about the body of the Moone, from which we may likewise argue an Atmo-sphæra, since we cannot well conceive what so probable a cause there should be of such an appearance as this,

Quod radii Solares à vaporibus Lunam ambientibus fuerint intercisi,

that the Sun beames were broken and refracted by the vapours that encompassed the Moone.

3. I may adde the like argument taken from another observation which will be easily tried and granted. When the Sunne is eclipsed, wee discerne the Moone as shee is in her owne naturall bignesse, but then she appeares somewhat lesse then when shee is in the full, though she be in the same place of her supposed excentrick and epicycle, and therefore Tycho hath calculated a Table for the Diameter of the divers new Moones. But now there is no reason so probable to salve this appearance, as to place an orbe of thicker aire, neere the body of that Planet, which may be enlightened by the reflected beames, and through which the direct raies may easily penetrate.