84 REPORT — 1853. 



conclusions. The source of fallacy I conceive to be this : — the base of the 

 cliff first yields to the attrition of the gravel and washing of the ocean ; thus 

 an undermining or'scooping process necessarily takes place, and for many 

 months or years a very large portion of what may be called table-land, is 

 held by an exceedingly precarious tenure ; so that it not unfrequently 

 happens that one or two severe storms take off several yards of surface 

 from any particular farm or district, and these losses are then recorded 

 as having occurred within a very limited time ; whereas, in truth and fairness, 

 they ought to have been spread over a number of years, commencing with 

 the washing away of the base. 



First Report of the Committee, consisting of the Earl of Rosse, the 

 Rev. Dr. Robinson, and Professor Phfllips, appointed by the 

 General Committee at Belfast, to draw up a Report on the Physical 

 Character of the Moon's Surface, as compared with that of the 

 Earth. 



I. The Committee, having received their instructions in September 1852, lost 

 no time in assembling, by invitation of the Earl of Rosse, at Parsonstown, 

 where with the assistance of Colonel Sabine, at that time President of the 

 Association, they made preliminary examinations of the moon, by the power- 

 ful telescopes of the Earl of Rosse, and formed plans of further proceeding in 

 conformity with the results of these examinations, and the individual expe- 

 rience of the members of the Committee. 



II. Taking as a general basis for the work to be done, the much-valued 

 maps and treatise of Madler and Beer, it appeared to the Committee desirable 

 to procure a new set of drawings or surveys of selected parts of the lunar 

 disc ; to suggest certain conditions of representation, with reference to the 

 illumination of these parts, and to propose a uniform scale for the drawings. 



The suggestions offered, as some help to observers on this subject, were 

 the following : — 



" 1. For the acquisition of correct Ideas regarding the form of any part 

 of the lunar disc, an examination of it under at least three aspects appears 

 indispensable. 



a. A little (one hour ?) after the sun rises on that part of the spherical 

 surface. 



b. When the sun is on the meridian of that part. 



c. A little (one hour?) before the sun sets upon it. 



" By this arrangement each part of the surface may be delineated and de- 

 scribed under three directions of incident sun-light, two of them (a and c) 

 suited by long shadows to discover the inequalities of level, and the other 

 (U) aiding by a vertical incidence to make apparent the unequal reflective 

 powers and different colours which characterize the different lunar regions, 



