April 1, 1898.] 



KNOWLEDGE, 



85 



is a reproduction of plate No. 6 in the Observatory Atlas of 

 the Moon in course of publication by the Mount Hamilton 

 Observatory, the original negative of which was secured 

 April 9th, 1897 ; moon's age, eight days. 



The reader will hardly need to be reminded, ere we 

 proceed with our brief description, that the Lick and Paris 

 Observatories are each publishing atlases in which the 

 original photogpraphs taken at the respective institutions 

 are moderately enlarged. A third publication is that of 

 Prof. Dr. Weinek, in which the magnification is pushed 

 a good deal farther in the able hands of this most 

 skilful selenographer. Last comes the atlas of Herr 

 Krieger, who has deftly inserted details at the telescope, 

 using existing photographs as a guide. A comparison of 

 these various methods and results is deeply interesting and 

 instructive, and these atlases between them must immensely 

 advance our knowledge of the moon. 



The scale of the accompanying photograph is not large 

 enough to bring out those minutiie which have such interest 

 for selenographers, and which at times give rise to lively 

 and even acrimonious discussion. But though detail be 

 wanting, the picture shows — very nearly as well as though 

 the reader were actually peering through the eyepiece — the 

 broad lines of lunar landscape, which are perhaps as 

 important in the framing of hypotheses as the minute 

 objects amongst which the wielder of high powers is always 

 so happy to revel. 



Our key-chart will render easy the identification of the 

 various objects in the photograph. The sun is just rising 



on the western ramparts of Plato, and is throwing the 

 Alps, Caucasus, and Apennines into splendid relief, all the 

 more marked because of the sombre plain from which they 

 rear their crests. Let us look for an instant at the great 

 craters which the photograph includes. 



The largest is Aristoteles, and somewhat to the south 



the smaller but still immense Eudoxus. Aristoteles is no 

 less than sixty miles in diameter, and its walls rise to a 

 maximum height of eleven thousand feet above the floor. 

 It is, however, but imperfectly seen in the illustration, for 

 the camera cannot be prevailed on to show objects exactly 

 as they appear to the eye, introducing a glare here and a 

 blackness there which detract somewhat from its inestim- 

 able value. 



The splendid ring of Archimedes is described by Elger 

 as " next to Plato the finest object on the Mare Imbrinm." 

 It is fifty miles in diameter, but the walls are less lofty 

 than those of Aristoteles. Still, the shadows show out 

 splendidly as sunrise progresses, whilst about the lunar 

 noon a curious system of craterlets and light streaks is 

 revealed, reminding one of the interior of Plato. 



To the north-west of Archimedes lie Autolycus and 

 Aristillus • — stately names aU three ! Both the latter 

 are the centres of minor ray systems, and Aristillus is 

 " flanked on all sides " (as Webb tells us) " by radiating 

 banks resembling lava streams, or currents of ejected 

 blocks or scorin}," of which there is just a faint trace in 

 the illustration. On its eastern side Aristillus is eleven 

 thousand feet deep. 



To the north, between the Alps and Caucasus, is the 

 interesting crater plain Cassini, which will afiford the lunar 

 draughtsman many hours of pleasant work ; and he may 

 afterwards compare advantageously his drawings with the 

 photographs in Knowi,ei>(;e and elsewhere. 



Towards the north pole of the moon we have quite a 

 crowd of craters, confused by foresbortenin;,', but forming 

 a very poor second to the tremendous display near the 

 southern extremity of the axis. 



Most of these objects have but feeble terrestrial analo- 

 gies, but when we turn to the lunar mountain ranges we 

 seem on more familiar ground. And what a glorious 

 spectacle would stretch before the observer could he but 

 stand on one of these lofty peaks — on Mont Blanc (twelve 

 thousand feet). Mount Wolf (eighteen thousand feet), or 

 Caucasus (nineteen thousand feet) ! What a bewildering 

 panorama would it not be — a " nightmare vision," as one 

 writer calls it, only to be imagined in our dreams ! 



Perhaps the great mountain ranges are the most satis- 

 factorily depicted of any objects on the photograph before 

 us. They will bear long looking at, but must of course be 

 seen in the telescope to appreciate their full magnificence. 



The eye will not be long before it rests on that very re- 

 markable object, the great valley of the Alps. This mighty 

 gash, as though the work of some gigantic axe, is above 

 eighty miles long, and to be distinctly seen in all but the 

 feeblest telescopes. Only from four to six miles broad, its 

 walls tower up for well-nigh twelve thousand feet. At its 

 southern end it opens out into a noble amphitheatre. Webb, 

 Elger, and others have studied and drawn this wonderful 

 valley, and two of Mr. Elger's drawings enrich the Jouninl 

 of the Lirt-r/iool Astinwrnical Societi/. The lunar members 

 of the British Astronomical and other Associations might 

 well turn to the great Alpine valley as a change from the 

 bewildering spots, craterlets, and streaks of more frequently 

 delineated objects. 



^- 



Notftgg of ISooitg. 



A Treatise on Chemistry. By Sir Henry Koscoe and 

 C. Schorlemmer, f.r.s. Vol. II. — " The Metals." (Mac- 

 mUlan.) Illustrated. 31s. 6d. Nineteen years have now 

 elapsed since the publication of the first edition of this 

 treatise, and in consequence of the many innovations in 

 the chemistry of the metals during that period, the 

 present edition (the third) may be regarded as a new 



