256 The Lunar Taurus (8.) and Argceus. 



N.W. side, the most remarkable region in the whole of his 

 Section III., which forms a square of about twenty-five lunar 

 degrees. Attention had been previously drawn to it, however, 

 by Schroter. In his first observation, 1788, November 4, he 

 describes it as a straight chain of five summits, divided by 

 parallel ravines, about thirty-seven miles long, and of a greyish 

 colour. This, contrary to the usual rule, he found brighter 

 when nearer the terminator, 1791, December 30, at which 

 time he ascertained the heights of each of the summits : that 

 furthest to the S.W. cast no "measurable shadow ; the others 

 ascended gradually through successive heights of 1980, 3170, 

 and 6570, to 10,190 feet at the opposite extremity of the 

 range, where it drops at once in a vast and awful precipice to 

 the plain beneath it, as is shown by the extraordinary straight- 

 ness of the 1ST. side of its spire of shade, and the perpendicu- 

 larity of its direction towards the terminator. Hence Schroter 

 justly remarks that the materials of the moon must be, at 

 least in part, as coherent as those of our globe ; and adds : 

 " Cliffs, in our terrestrial mountains, of even 200 to 300 feet 

 and upwards, from which we look down into the valleys lying 

 beneath them, make a powerful impression upon the suscep- 

 tible observer of the works of God. What a vast nature-scene 

 now would not open itself fully to mortal eye ? And how 

 great, beyond all imagination great, would not the impression 

 be, if it could gaze away from the steeply set-off peak upon 

 the soft lunar plains of the M. Serenitatis and M. Tranquilli- 

 tatis ?" Another measure, 1796, August 9, under less favour- 

 able circumstances, gave him 11,490 feet, the shadow being 

 then very differently shaped and directed — a variation which 

 he was disposed to ascribe to atmospheric obscuration, but 

 which might more naturally be referred to irregularities in the 

 surface of the plain below. In two other observations he again 

 saw it straight-edged, but shorter, and cut off square at the 

 end. 



On two occasions only have I any record of having observed 

 this magnificent precipice ; the former, 1855, November, 14 d. 

 6 h., the moon being 5 d. old, and 3 d. 14 h. past the greatest 

 S.E. libration, when, notwithstanding a very low position and 

 dim and agitated image, I could perceive a grand pointed mass 

 of shadow ; the latter, 1858, February, 18 d. 7 h. 45 m. — 4d. 

 2H h. after new, 4 d. 4 h. after greatest N.E. libration. The 

 distance of the terminator at this time from the N.E. end of 

 the range was about equal to its length ; and the great steep- 

 ness of the enormous cliff was finely shewn by the very- 

 straight edge of its shadow, cast across the plain to the termi- 

 nator, by which, though already narrowing in rapidly, it seemed 

 to be truncated; only 1 h. 15 m. later, the spire of shade 



