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Schröter's final result in 1811 was 23h. 21m. 7·977s. Monat. Not., vol. lvii., p. 402; Astr. Phys. Roy. Astr. Nach., No. 2,021; Am. Spettr. Ital., Dicembre, 1882; Am. Ass., 1873, p. 407. Nach., No. 2,809; f. Nach., No. 3,097; Phil. Trans., vol. clxxxvi., A., p. 469; Proc. Roy. Geol. Soc., vol. iii. Mag., vol. xxviii. Wien, Bd. lxiv.; quoted by Poynting. Cf. The Moon, by T. Gwyn Elger, p. 20.
Thomas Gwyn Elger has this to say on the subject of the lunar clefts: "If, as seems most probable, these gigantic cracks are due to contractions of the moon's surface, it is not impossible, in spite of the assertions of the text-books to the effect that our satellite is now a 'changeless world, that emanations may proceed from these fissures, even if, under the monthly alternations of extreme temperatures, surface changes do not now occasionally take place from this cause also.
The ring mountain Landsberg, on the equator, and near the center of the visible eastern hemisphere, is worth watching because Elger noticed changes of color in its interior in 1888. Bullialdus, in the midst of the Mare Nubium, is a very conspicuous and beautiful ring mountain about thirty-eight miles in diameter, with walls 8,000 feet high above the interior.
Not water, but perhaps a sea of lava which has now solidified and forms the floor of the Mare Nectaris. The name of this singular formation is Fracastorius. Elger has an interesting remark about it.
Elger, who was a most industrious observer and careful interpreter of lunar scenery, speaks of "the undoubted existence of the relics of an earlier lunar world beneath the smooth superficies of the maria."
Should this be so, the appearance of new rills and the extension and modification of those already existing may reasonably be looked for." Mr. Elger then proceeds to describe his discovery in 1883, in the ring-plain Mersenius, of a cleft never noticed before, and which seems to have been of recent formation.
As an encouragement to amateur observers who may be disposed to find out for themselves whether or not changes now take place in the moon, the following sentence from the introduction to Professor Pickering's chapter on Plato in the Harvard Observatory Annals, volume xxxii, will prove useful and interesting: "In reviewing the history of selenography, one must be impressed by the singular fact that, while most of the astronomers who have made a special study of the moon, such as Schroeter, Maedler, Schmidt, Webb, Neison, and Elger, have all believed that its surface was still subject to changes readily visible from the earth, the great majority of astronomers who have paid little attention to the subject have quite as strenuously denied the existence of such changes."
Elger remarks of this theory that the "confused network of streaks" around Copernicus seems to respond to it more happily than the rays of Tycho do, because of the lack of definiteness of direction so manifest in the case of the rays.
T. G. Elger, the celebrated English selenographer, says of Plinius that, at sunrise, "it reminds one of a great fortress or redoubt erected to command the passage between the Mare Tranquilitatis and the Mare Serenitatis." But, of course, the resemblance is purely fanciful. Men, even though they dwelt in the moon, would not build a rampart 6,000 feet high!
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