300 



REPORT 1865. 



increased in value by the existence of records such as Schroter's, Lohrmann's, 

 and Beer and Madler's. Lohrmann's sections, with the text, may be placed 

 in the same category as Schroter's, and his map, with 500 reference-numbers, 

 but no text, including a very large amount of detail, furnishes material by 

 which the selenographer may confirm his observations, or by means of it, 

 objects may be indicated that may have been overlooked, or possibly may 

 even be new. Beer and Madler's large map is of the same character as 

 Lohrmann's, but with this advantage, notices of the features on the map (to 

 which reference-letters, Roman, Italic, or Greek, are attached) are to be 

 found in the text, affording, with the results of previous labours in the same 

 field, a large amount of existing material to catalogue ; for it is evident that 

 features found on the maps and drawings, and referred to in the text, had a 

 bond fide existence, and were subjects of observation at the three several 

 epochs. The later and smaller map of Madler is also valuable for reference. 

 In order to ensure the insertion of these objects in the catalogue, four 

 columns (17, 18, 19> and 20), having suitable headings, are appropriated 

 to references to these authorities, the reference-letters and figures being 

 given when available ; and in other instances, where the objects are found in 

 the maps or engravings, but without any reference-letters or figures, a dash 

 ( — ) is inserted, the absence of a dash against any object indicating that it is 

 not to be found in the records of the selenographer whose name is at the head 

 of the column. 



Of all the aids that we possess to the attainment of a valuable and exten- 

 sive knowledge of the moon's surface, none are calculated to afford such accu- 

 rate results, so far as mapping, symbolizing and cataloguing are concerned, 

 as photography. The large number of negatives produced by Warren De la 



Rue, Esq. 



and the enlargement of 



them both on glass and paper, must 



become of much valuable assistance in the progress of this work. The true 

 relative positions of objects are capable of being very readily determined, 

 and when reference is made to the normal position of mean libration, — the 

 photograph taken on October 4, 1865, at 9 h m 4 s mean time, at Cranford 

 being a standard in this respect, — the photographs will contribute in no small 

 degree to accurate mapping and symbolizing ; other important data are also 

 obtainable by their means. In order to ensure a careful comparison of all 

 existing records with the results of photography, a column (21) is inserted, 

 and headed " De la Rue," in which every object found on the photographs is 

 indicated by a dash ( — ). 



[Form No. 4.] British Association for the Advancement of Science. — 



(Lunar Committee.) 

 Form for computing t7ie Positions of Lunar Objects (the Second Order). 



Tan <4 = 



Y-Y' 

 X-X' 



1 = 



X-X' 



Cos <p 



x= 

 x = 



Log. (X-X') 



Log. Tan ip 

 Log. Cos <j> 

 Log. 1 



Y= 

 Y'= 



Log. (T-l , 

 1 = 



O / ft 



