Views of astronomy : seven lectures delivered before the Mercantile Library Association of New York in the months of January and February, 1848 / by J.P. Nichol ; reported for the New-York Tribune by Oliver Dyer.
- John Pringle Nichol
- Date:
- 1848
Licence: Public Domain Mark
Credit: Views of astronomy : seven lectures delivered before the Mercantile Library Association of New York in the months of January and February, 1848 / by J.P. Nichol ; reported for the New-York Tribune by Oliver Dyer. Source: Wellcome Collection.
Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)
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![efit which Astronomical observations might bestow upon Geology that the Moon negatives this expla- nation at once, for on this orb, as we have said, no liquid exists and has never been. Bat the prevalent lorm of elevation belongs to neither class. At least two-fifths of the surface of our Luminary are studded with profound caverns penetrating its body, and generally engirt at the top by a great wall of rock which is surmounted or crowned by lofty peaks. These caverns, or, as they have been termed, craters, vary in diameter from fifty to sixty miles to the smallest space visible, probably one hundred and fifty feet; and the num- bers increase as the distance diminishes, so that the multitute of the small ones passes enumeration. In order to impress upon you what these objects are let us pay a visit to one of them, say the crater of Tycho. As we approach the crater we will find a very rough country. Our first glance would be arrested by a wall of solid rock appearing in the horizon stretching fifty miles away. As we ap- proach we will find this wall sloping up to the night of about 3,000 feet. Suppose we ascend. What do we expect to see on the other side—a slope ? On the contrary, when we arrive at the top, we find ourselves on the brink of a precipice that in one leap goes down 13.000 feet! Then we discover below that enormous depth some similar ranges of moun tains, lying like terraces and stretching round the base of the wall, and a little onward beyond these lies the bottom of the chasm which is 17,000 feet from where we stand. The diameter of the cavern is about fifty-five miles. If a person were standing down in its center he would see on every side, at a distance of twenty-five miles, an appalling preci- pice rising up 17,000 feet—2,000 feet higher than Mont Blanc. If there are any inhabitants there they must have some means of locomotion with which we are unacquainted. (Laughter and ap plause.) Such then is Tycho, and precisely of this kind are all the craters in the Moon. Many of them are not so de,ep, some of them are deeper. Some in the southern part of the Moon are said to be so deep that we can never see the bottom. Whether this be so or not there are several 3,000 feet in diameter and as deep as Tycho. Now it is evident on the very first glance that even our largest volcanic craters are not to be com- pared with these caverns of the Moon. The largest we have any knowledge of is in the South Sea Isl- ands, but that is comparatively small and is situa- ted at the top of a mountain. In order to discern aaght similar upon the Earth, then, we must look to larger displays of the disrupting energy. [The Lecturer here drew a diagram of a group of mountains among the Alps, exhibiting the cir- cular formation but differing from Lunar Craters in two points. In the first place the range is bro- ken by gaps; and secondly, the interior is not a pit, but, on the contrary, rather higher than the ex- ternal surface of the Earth. He showed then bow these might be explained by the presence of the meteorological agents—rain, fro3t, wind. etc.—on the Earth, which are not present in the Moon : and interpreting them by tbis principle it seemed that the older otdur terrestial mountain formations ren- dered it likely that the crater form did, in the ear- lier epochs of the Earth's geological history, prevail likewise here.] May it not then be that the Moon is simply in a comparatively early epoch of its developement? That, as the Nebular hypothesis would seem to establish, the Lunar globe is younger than the Earth j and that with regard to it, also, a time may come when the upheaving cause will manifest itself principally,—as now in tne Earth—by upheaving ranges and groups of mountains instead of craters? This is probably all that we can derive from a view of this portion of the subject. To proceed with our subject, can we form aDy idea regarding the nature of the power which could produce craters like Tycho ? There is a feature connected with this crater which, in this respect, is of high importance. I mean those broad bands which issue from it and go across the surface of the Moon even to the distance, in one case at least, of 1,700 miles. [The Lecturer here went through a minute investigation of the characteristics of these bands, chiefly by means of diagrams on the black- board, and elaborate paintings, which we regret we cannot give. He seemed to render it probable that, like our own trap-dykes, these bands consist of matter which muse have come up from the inte- rior of the Moon's mass through cracks in its solid crust. Now as these cracks must have been formed by the convulsion which produced Tycho, this convulsion, then, must have been sudden as well as most violent, at once producing the cavern itself and cracking the Moon in the manner in which we see it. The phenonema here indeed cannot be reconciled to any gradual operation or the action of any force long continued. It must have been as sharp as violent; instantaneous after the manner of an explosion. The imagination, habituated to the comparative quiet of our time, cannot easily reach the conception of a convulsion like this. Let my audience not discredit or doubt the speculation because of the fancied oddness or the gigantic character of the force whose action it presumes. So far from being impossible, the like of it, in part at least, has passed during the pro- press of time in almost every region of our globe. It is clear and perfectly indisputable, that when our own granitic ranges were pushed from the Earth's interior they bore up along with them many miles of rock of vase thickness that once lay quiet at the bottom of the ocean, and over which shell-fish crept, that are now entombed within their layers.. Such convulsions were indeed often slow, and may have have occupied ages in their progress of completion, for the rocks that were disturbed are frequently little confused, lying around the central granitic mass as a graceful robe; but go with me to the Alps, or even to our own English Cumberland, or North Wales, and I could show you masses above masses which, when they were formed, lay as flat and even as the surface of that floor, not only turned from their repose and tilted upward in the air, but, by the violence of the action that disturbed them, rolled over each other in con- fused heaps, presenting for miles together to the puzzled explorer the aspect of a crumpled and crushed sheet of paper. Yes! there, indeed, has been power, immeasurable, scarce even conceiva- ble ; but the giant Earthquake has an arm capable of all this work. (Great applause.) I would now, ladies and gentlemen, for one mo- ment digress from our course and inquire, if the force that formed Tycho was so great, what be- came of the rocks that it blew out of Tycho? A cavern of that kind, fifty-five miles in diameter, is not an infinitessimal thing which may be easily formed. What became of these rocks 1 The most ready answer is that they returned again to the surface of the Moon, just as matter thrown Irom the Craters of our Volcanoes returns again to the Earth. There are circumstances, however, I think, that will induce us to pause before we assert that this took place. In the first place, the Moon being a small body does not exert much attractive power over a mass, therefore it would not take much force to drive away a body from the Moon altogether, aud send it](https://iiif.wellcomecollection.org/image/b21143821_0037.jp2/full/800%2C/0/default.jpg)
