Observ. [LIX]. Of multitudes of small Stars discoverable by the Telescope.

Having, in the last Observation, premis’d some particulars observable in the medium, through which we must look upon Cœlestial Objects, I shall here add one Observation of the Bodies themselves; and for a specimen I have made choice of the Pleiades, or seven Stars, commonly so called (though in our time and Climate there appear no more then six to the naked eye) and this I did the rather, because the deservedly famous Galileo, having publisht a Picture of this Asterisme, was able, it seems, with his Glass to discover no more then thirty six, whereas with a pretty good [Schem. 38.] twelve foot Telescope, by which I drew this 38 Iconism, I could very plainly discover seventy eight, placed in the order they are ranged in the Figure, and of as many differing Magnitudes as the Asterisks, wherewith they are Marked, do specifie; there being no less then fourteen several Magnitudes of those Stars, which are compris’d within the draught, the biggest whereof is not accounted greater then one of the third Magnitude; and indeed that account is much too big, if it be compared with other Stars of the third Magnitude, especially by the help of a Telescope; for then by it may be perceiv’d, that its splendor, to the naked eye, may be somewhat augmented by the three little Stars immediately above it, which are near adjoyning to it. The Telescope also discovers a great variety, even in the bigness of those, commonly reckon’d, of the first, second, third, fourth, fifth, and sixth Magnitude; so that should they be distinguish’d thereby, those six Magnitudes would, at least, afford no less then thrice that number of Magnitudes, plainly enough distinguishable by their Magnitude, and brightness; so that a good twelve foot Glass would afford us no less then twenty five several Magnitudes. Nor are these all, but a longer Glass does yet further, both more nicely distinguish the Magnitudes of those already noted, and also discover several other of smaller Magnitudes, not discernable by the twelve foot Glass: Thus have I been able, with a good thirty six foot Glass, to discover many more Stars in the Pleiades then are here delineated, and those of three or four distinct Magnitudes less then any of those spots of the fourteenth Magnitude. And by the twinkling of divers other places of this Asterisme, when the Sky was very clear, I am apt to think, that with longer Glasses, or such as would bear a bigger aperture, there might be discovered multitudes of other small Stars, yet inconspicuous. And indeed, for the discovery of small Stars, the bigger the aperture be, the better adapted is the Glass; for though perhaps it does make the several specks more radiant, and glaring, yet by that means, uniting more Rays very near to one point, it does make many of those radiant points conspicuous, which, by putting on a less aperture, may be found to vanish; and therefore, both for the discovery of the fixt Star, and for finding the Satellites of Jupiter, before it be out of the day, or twilight, I alwayes leave the Object-glass as clear without any aperture as I can, and have thereby been able to discover the Satellites a long while before; I was able to discern them, when the smaller apertures were put on; and at other times, to see multitudes of other smaller Stars, which a smaller aperture makes to disappear.

In that notable Asterism also of the Sword of Orion, where the ingenious Monsieur Hugens van Zulichem has discovered only three little Stars in a cluster, I have with a thirty six foot Glass, without any aperture (the breadth of the Glass being about some three inches and a half) discover’d five, and the twinkling of divers others up and down in divers parts of that small milky Cloud.

So that ’tis not unlikely, but that the meliorating of Telescopes will afford as great a variety of new Discoveries in the Heavens, as better Microscopes would among small terrestrial Bodies, and both would give us infinite cause, more and more to admire the omnipotence of the Creator.

Observ. [LX]. Of the Moon.

Having a pretty large corner of the Plate for the seven Starrs, void, for the filling it up, I have added one small Specimen of the appearance of the parts of the Moon, by describing a small spot of it, which, though taken notice of, both by the Excellent Hevelius, and called Mons Olympus (though I think somewhat improperly, being [Schem. 38.]
Fig. X, &c. rather a vale) and represented by the Figure X. of the 38. Scheme, and also by the Learn’d Ricciolus, who calls it Hipparchus, and describes it by the Figure Y, yet how far short both of them come of the truth, may be somewhat perceiv’d by the draught, which I have here added of it, in the Figure Z, (which I drew by a thirty foot Glass, in October 1664. just before the Moon was half inlightned) but much better by the Reader’s diligently observing it himself, at a convenient time, with a Glass of that length, and much better yet with one of threescore foot long, for through these it appears a very spacious Vale, incompassed with a ridge of Hills, not very high in comparison of many other in the Moon, nor yet very steep. The Vale it self ABCD, is much of the figure of a Pear, and from several appearances of it, seems to be some very fruitful place, that is, to have its surface all covered over with some kinds of vegetable substances; for in all positions of the light on it, it seems to give a much fainter reflection then the more barren tops of the incompassing Hills, and those a much fainter then divers other cragged, chalky, or rocky Mountains of the Moon. So that I am not unapt to think, that the Vale may have Vegetables analogus to our Grass, Shrubs, and Trees; and most of these incompassing Hills may be covered with so thin a vegetable Coat, as we may observe the Hills with us to be, such as the short Sheep pasture which covers the Hills of Salisbury Plains.

Up and down in several parts of this place here describ’d (as there are multitudes in other places all over the surface of the Moon) may be perceived several kinds of pits, which are shap’d almost like a dish, some bigger, some less, some shallower, some deeper, that is, they seem to be a hollow Hemisphere, incompassed with a round rising bank, as if the substance in the middle had been digg’d up, and thrown on either side. These seem to me to have been the effects of some motions within the body of the Moon, analogus to our Earthquakes, by the eruption of which, as it has thrown up a brim, or ridge, round about, higher then the Ambient surface of the Moon, so has it left a hole, or depression, in the middle, proportionably lower; divers places resembling some of these, I have observ’d here in England, on the tops of some Hills, which might have been caus’d by some Earthquake in the younger dayes of the world. But that which does most incline me to this belief, is, first, the generality and diversity of the Magnitude of these pits all over the body of the Moon. Next, the two experimental wayes, by which I have made a representation of them.

The first was with a very soft and well temper’d mixture of Tobacco-pipe clay and Water, into which, if I let fall any heavy body, as a Bullet, it would throw up the mixture round the place, which for a while would make a representation, not unlike these of the Moon; but considering the state and condition of the Moon, there seems not any probability to imagine, that it should proceed from any cause analogus to this; for it would be difficult to imagine whence those bodies should come; and next, how the substance of the Moon should be so soft; but if a Bubble be blown under the surface of it, and suffer’d to rise, and break; or if a Bullet, or other body, sunk in it, be pull’d out from it, these departing bodies leave an impression on the surface of the mixture, exactly like these of the Moon, save that these also quickly subside and vanish. But the second, and most notable, representation was, what I observ’d in a pot of boyling Alabaster, for there that powder being by the eruption of vapours reduc’d to a kind of fluid consistence, if, whil’st it boyls, it be gently remov’d besides the fire, the Alabaster presently ceasing to boyl, the whole surface, especially that where some of the last Bubbles have risen, will appear all over covered with small pits, exactly shap’d like these of the Moon, and by holding a lighted Candle in a large dark Room, in divers positions to this surface, you may exactly represent all the Phænomena of these pits in the Moon, according as they are more or less inlightned by the Sun.

And that there may have been in the Moon some such motion as this, which may have made these pits, will seem the more probable, if we suppose it like our Earth, for the Earthquakes here with us seem to proceed from some such cause, as the boyling of the pot of Alabaster, there seeming to be generated in the Earth from some subterraneous fires, or heat, great quantities of vapours, that is, of expanded aerial substances, which not presently finding a passage through the ambient parts of the Earth, do, as they are increased by the supplying and generating principles, and thereby (having not sufficient room to expand themselves) extreamly condens’d, at last overpower, with their elastick properties, the resistence of the incompassing Earth, and lifting it up, or cleaving it, and so shattering of the parts of the Earth above it, do at length, where they find the parts of the Earth above them more loose, make their way upwards, and carrying a great part of the Earth before them, not only raise a small brim round about the place, out of which they break, but for the most part considerable high Hills and Mountains, and when they break from under the Sea, divers times, mountainous Islands; this seems confirm’d by the Vulcans in several places of the Earth, the mouths of which, for the most part, are incompassed with a Hill of a considerable height, and the tops of those Hills, or Mountains, are usually shap’d very much like these pits, or dishes, of the Moon: Instances of this we have in the descriptions of Ætna in Sicily, of Hecla in Iceland, of Tenerif in the Canaries, of the several Vulcans in New-Spain, describ’d by Gage, and more especially in the eruption of late years in one of the Canary Islands. In all of which there is not only a considerable high Hill raised about the mouth of the Vulcan, but, like the spots of the Moon, the top of those Hills are like a dish, or bason. And indeed, if one attentively consider the nature of the thing, one may find sufficient reason to judge, that it cannot be otherwise; for these eruptions, whether of fire, or smoak, alwayes raising great quantities of Earth before them, must necessarily, by the fall of those parts on either side, raise very considerable heaps.