ON THE PHYSICAL ASPECT OF THE MOON. 181 



both drawings ; but Prof. Phillips continues it further to the south, even info 

 the crater marked A, which is likewise traversed bj' the longest rill of all, 

 that, viz., nearest to Campanus. Another rill is traced by Prof. Phillips quite 

 across and through the old crater of Hippalus ; and all the rills appear to him 

 to be rifts or deep fissures, receiving strong shadows from oblique light, and 

 even acquiring brightness on one edge of the cavity. Their breadth appears 

 to be only a few hundred feet or yards. He exhibited drawings of these 

 objects on a large scale, one being a section across the crater of Gassendi, 

 another a map of the curious region extending from Aristarchus and Hero- 

 dotus along the interrupted rift or valley which opens by a seeming delta 

 into the seeming dried sea-bed with indented coasts on the south. 



Speaking of Gassendi, of which he had made drawings under different 

 conditions of light and shade, from sunrise on the mountains to mid-day, 

 and slighter, sketches at later hours, he remarked, in addition to what has 

 been recorded by Miidler, the much-varied character of the ' rings,' the deep 

 narrow fissures across the ring on the S.E. side, the rocky character of the 

 central elevations in the interior area, the rough terraces and ridges within 

 the great ring on the east and also the north-west side, the occurrence of 

 only two small craters in the northern part of the area, and the variation of 

 colour on the surface, without shadow, according to the change of the angle 

 of incidence of the sun's rays. 



He also drew attention to the existence of delicate ramifications of small 

 ridges and hollows in the S.VV. part of the ai-ea, which had a marked con- 

 vergence towards the broad lip of the deep-attached cavity known as the 

 Spoon. He expressed his great desire to receive drawings of Gassendi as 

 Been at iioou and at later hours of the lunar dav. 



Contribution to a Report on the Physical Aspect of the Moon. 

 By W. R. BiRT, F.R.A.S, 

 On the present occasion I propose confining my contribution to the physical 

 features characterizing the well-known spot Plato, some of which are fami- 

 liar to astronomers, while others, I have some reason to believe, have not 

 hitherto been pointed out. I have included all that have come under obser- 

 vation during the twenty-nine months between January 1860 and May 1862, 

 inclusive, in a synopsis of objects suitable for further telescopic observation. 

 This synopsis of objects is necessarily incomplete. To each object observed 

 I have appended, in italics, the number of times it has been the subject of 

 special observation ; so that every one inserted in the key-plan has been seen 

 by me at some time during the interval of the observations above mentioned. 

 The entire period of the visibility of Plato is embraced in the observations, 

 which are, however, more numerous under the morning and mid-day illumi- 

 nations than under the evening. Those features that have been more fre- 

 quently observed may of course be regarded as being more fully established, 

 at least for the period embraced by the observations; the synopsis forming a 

 groundwork for the more effectual observation of Plato, especially as re- 

 gards the interesting questions of absolute repose now existing on the moon's 

 surface, or the progress of change such as may be detected by human eyes. 

 Forty-five series of observations contributing to the synopsis, and extending 

 from January 5, 1860, to July 29, 1861, I have arranged in the order of the 

 moon's age, in a MS. volume which is deposited in the library of the lloyal 



