miles: but that of the hills is no more than a few miles. Snowden in Caernarvonshire (the highest mountain in all our ifland) is but 1247 yards;' the Alps themselves but about two English miles *; nay, the very pike of Teneriffe, one of the highest ridges throughout the globe (unless we except the high mountains of Peru, called by Jof. Acofta y Periacaca; "In the journal of the late ingenious Richard Townley Efq; of Townley in Lancashire, I find this note upon Sept. 6, 1682. This day Mr. Adams called here, who is taking a furvey, &c. He told us, that with repeated trials he had found Snowdon-hill 1320 yards higher then the high-water-mark, and that the quick filver ftood at the bottom at 29 Inches; at the top of the hill 25'96; fo that 1320 gave 3'04. Then follows this note, viz. Mr. Adams coming fince, tells me, that the height of Snowdon was but 1247 yards, which gave 3'04. The reafon of this difference of 73 yards, in the height of Snowdon, I take to be, that the first measure was made by Mr. Adams himself, the latter by Mr. Cafwell, with Mr. Adams's inftruments: and probably the former is the height above the fea, the latter only above fome plane. * Mr. Nich. Facio told me, that he had measured the height of the Montagne Mauditi, which is one of the highest ridges of the Alps, and that he found it to be 2000 French toifes above the Lake of Geneva, which is equal to 12816 English feet, or 2'42 miles. Acofta faith, the Alps feemed to these mountains he travelled over, but as ordinary houses to lofty towers. See my Phyf. Theol. B. I. Ch. 1. Note (w) 1 Capt. Periacaca or that near St. Martha 2; ; or those called the Andes ;) this ridge, I fay, is computed to be but between three and four miles perpendicularly above the fea. All which eminences, compared with the diameter or femidiameter of the earth, is no more than as a particle of duft to a large globe on which it refteth. And fo likewife for the mountains vifible in the Moon, although fome of them are of that height as to reflect the light of the Sun from their lofty tops, 2 Capt. Dampier faith, that he is of opinion that the hill near St. Martha is higher than the pike of Teneriffe. See Voyage round the World, p. 24. * Of the Andes of Chili and Peru, Capt. Dampier faith, these are the highest mountains I ever faw, far furpassing the pike of Teneriffe, or Santa Martha, and I believe, any mountains in the world. Ibid. p. 99. See Dr. Hooke's account of the pike of Teneriffe, from his friend Mr. G. T. who went to the top of it; at the end of his lectures concerning fprings, p. 42. 'By Riccioli's meafures, the height of what he calls Mount Sinai, or St. Katharine's Hill, is nine Bononian miles, and that of Xaverius 12; but according to his corrections, the former is but 8 miles, the latter 114. Which at the rate of 6020 English feet in a Bononian mile, is about 13 and 9 English miles; an height fo great, confidering how much the moon is lefs than the Earth, that I cannot but think that diligent person was mistaken in his measures, and that the computations of Hevelius are much the best; who, as he was as able as any man, and made more accurate and diligent obfervations of the Moon's face, than moft men ever did, fo he was more likely to come nearest the truth. And by his reckoning, the highest hills in the moon are but about three quarters of a German mile, and fome of them but feven fixteenths, and fome not above an Italian mile. And confidering the bulk of the Moon to that of the Earth, these are great eminences for the Moon. And as the lunar mountains are of fuch prodigious heights, fo many of them are of great extent. Hevelius .reckons the Lunar Taurus to reach to 170 German miles; Mount Sepher 150; and the Lunar Appenine about 100 German miles. The way how to measure the height of the mountains of the Moon is not difficult, nor uncertain; which is, by obferving the diftance between the diftant golden fpots, at their first appearance (which are the tops of hills) and the enlightened part of the Moon. Which distance may be computed by miles, or any other equal parts, into which we can imagine the moon's diameter divided. Thus in Fig. 5. ARB is a part of the Moon's circumference, one part of which A R is enlightened, the other part R B is in darkness. Hi is a mountain, whose top H is touched by the Sunbeams, fhining from 8 the Sun to R, and reaching to H. Now fuppofing the femidiameter of the Moon, R C, to be 274 German miles, according to Hevelius, the length of the fide R H (or diftance between the top of the hill, and the edge of the enlightened part) will be found alfo to be a 10th, 20th, or other part of that femidiameter or diame. ter; or fome certain number of miles. And then we have the two fides RC 274 miles, and R H, and the right angle included between them; by which, both the other angles, and the fide CH, may be found by a common cafe of right angled triangles. Out of which fide C H, deducting the Moon's femidiameter 274, there remaineth the height of the mountain Hi. Confult here Hevel. Selenogr. Ch. viii. Galilæus Nunc. Sider. p. 53. Riccioli Almagest. L. iv. c. 8. Schol. tops, fome days before ever it reacheth the valleys beneath them, yet on the Moon's limb we can difcern nothing of them: but fo far from that, that, on the contrary, the edge through our best glasses looks like an even, fmooth, and uninterrupted circle . Although then vaft mountains, when feen near at hand, feem to be very confiderable excrefcences of our globe, yet fince they are little, when com The edge of the Moon, which I here mean, is that next the Sun; on which I could never perceive with my best glasses any the leaft fign of a mountain, but all to be exactly level and smooth. Only indeed there arè fome certain tranfient roughneffes and unevenneffes on the limb caufed by vapours, especially when the moon is near the horizon, and in windy, and in fome other weather. At which time the motion of the air and vapours makes a pretty crifpation and rolling, like waves, on the Moon's limb, which have the appearance of moving mountains and valleys. But on the oppofite fide, if the leaft portion of the darkened part of the Moon extends beyond the enlightened part, mountains may very manifeftly be difcerned, exactly refembling ours on the Earth. A few hours before and after the full, I have with pleasure feen the appearance of confiderable mountains and bays. One of which views I have given in Fig. 6. which is the Moon's appearance, foon after the full, on Sept. 12, 1714. In which feveral rifings and depreffions may be feen, and the tops of fome of the mountains fomewhat diftant are expressed by the little spots. Thefe alone I conceive are mountains which the excellent Hevelius fpeaks of in feveral places of his Selenography, particularly in his anfwer to Bettinus, and other Peripateticks, in Ch. vi. p 143. who denied that mountains could be in the Moon, as well as many other things difcovered now by the telescope. |