76 REPORT— 1869. 



Repm-t of the Lunar Committee for Mapping the Surface of the Moon. 

 Drawn up by W. R. Birt, at the request of the Committee, consisting 

 0/ James Glaisher, F.R.S., Lord Rosse^ F.R.S., Sir J. Herschel, 

 Bart., F.R.S., Professor Phillips, F.R.S., Rev. C. Pritchard, 

 F.R.S., W. HuGGiNs, F.R.S., W. R. Grove, F.R.S., Warren De 

 La nv^,F.R.S., C. Brooke, F.R.S., Rev. T. W.Webb, F.R.A.S., 

 Herr Schmidt, Admiral jNIanxers, President of the Royal Astro- 

 nomical Society, Lieut.-Col. Strange, F.R.S., and W. R. Birt, 

 F.R.A.S. 



In presenting the Eeport of the proceedings of the Lunar Committee re- 

 appointed at iSTor-ndch, it is desirable to refer as briefly as possible to the 

 progress of selenographical research during the entire existence of the 

 Committee. Since the Meeting of the British Association at Birmingham 

 four areas of the moon's surface, each of 5^ in extent both of longitude and 

 latitude, have been carefully and critically surveyed, not so much by the 

 determinations of positions (the means at the disposal of the Committee 

 being inadequate for instrumental and computative labour, which could only 

 be carried on in an establishment exclusively devoted to such an object, the 

 cost of which would far exceed the grants with which the Association has 

 aided the work) as in an examination of the physical aspects of 100 square 

 degrees of the moon's sm-face by means of the comparison and measurement 

 of photograms, combined with observation at the telescope, by several 

 observers in concert. Outlines of the objects thus siu-veyed have been laid 

 down on the orthographical projection on a scale of 200 inches to the moon's 

 diameter. The area thus survej-ed includes 443 objects ; a catalogue of 

 these objects has been prepared containing numerous selenographical and 

 selenological notices, those of the three areas completed previous to the re- 

 appointment of the Committee having appeared in the Appendices to the 

 Eeports of 1866 and ISGS. 



One of the principal objects which has been kept steadily in view is such 

 a description of lunar features that at any future time the similarity of the 

 description with the state of any particular crater, mountain, &c., or a depar- 

 ture therefrom, may be rcaddy ascertained. The great question of continued 

 lunar change, either transient or permanent, as contrasted with apparent 

 change dependent upon illuminating and visual angles, is one more likely for 

 posterity to settle. If, in geological science, a region undergoing a series of 

 changes (during the progress of which, through a long period of geological 

 time, lakes have been di'ained, volcanos have burst forth, extensive plateaus 

 of igneous ejections formed, and vast denudations of softer materials effected) 

 has retained its grander and more imposing features in their integrity, so in 

 selenological science we may look for small, and in many cases to us almost 

 inappreciable changes in and around weU-rccognized and imposing lunar 

 forms, than expect to witness the obliteration of some very striking object as 

 an evidence of change. The following are extracts from the catalogue of 

 the area completed during the past year. 



" The boundaries of Hipparchm differ materially from those of ordinary 

 walled plains, and the cliffs on the S.W. are very unlike those of a circular 

 form, inclosing large circidar plains, as may be seen in the neighboiulng 

 formation Ptolemaus. They present the appearance of having suffered 

 erosion, the character of the S.W. side of these cliffs beiug remarkably 

 different from the exteriors of large rings, craters, and plains. These 

 features, combined with the gradations of level observable in the floors of 



