294 report— 1865. 



In order to arrange the objects seen on the moon's surface in a systematic 

 and orderly manner, with a view to the formation of a catalogue, we must in 

 the first instance adopt some means by which we may so fix an object 

 observed that it may ever after in all time be sufficiently identified by all 

 future observers. Hevelius laid the foundation of this process, although the 

 nomenclature of his successor, Riccioli, has been grasped firmly by the astro- 

 nomical mind, so that the larger features and craters are now so readily 

 recognized, and in one way or another brought before the attention of astro- 

 nomers, that we should as soon expect to lose sight of Sirius, Lyra, Arcturus, 

 Capella, Regulus, or any of the brighter stars, as to experience any difficulty 

 in identifying Copernicus, Tycho, Plato, Hipparchus, Ptolemaeus, Gassendi, 

 the Mare Crisium, the Mare Nectaris, or any of the more conspicuous craters 

 and regions of the moon ; but as there are smaller stars in the heavens 

 requiring the aid of catalogues for their exact identification, especially when 

 used as comparison stars in the observations of small planets, comets, &c, 

 so in several questions connected with lunar physics, there are small objects, 

 forming in many instances portions of the larger features, that require to be 

 particularly specified, especially when questions of sujiposed change obtrude 

 themselves and claim a hearing, a small crater or apparently insignificant 

 mountain being adduced as evidence. In the present state of selenography 

 we cannot say positively of any object " it is new." All questions of this 

 kind that may be raised must be left in doubt. Astronomical juries cannot 

 agree on their verdicts. A great authority thus expressed himself: — " Al- 

 though not in a position myself, after twenty-five years' close observations of 

 this kind, to bring forward even one certain example of new formation, when 

 the question is confined to crater forms, yet I am far from disputing the fact 

 of the existence of new formations on the moon" *. Close and systematic 

 record, as well as close and unremitting observation, is necessary to be able 

 to settle a question of this kind, and the record shoxdd embrace the results of 

 the observations of all observers. The symbols alluded to under the head of 

 Form No. 2, to be inserted in column 2 of Form No. 3 (see page 296), appear 

 to be suitable for accomplishing this object; more than 1000 lunar objects 

 being absolutely fixed as to all future identification by their means, provided 

 certain elements, hereafter to be named, are ascertained. 



The next step in the formation of a catalogue is the determination of the 

 exact positions of the objects symbolized. This has been done with more 

 or less accuracy in numerous instances,'the coordinates (latitudes and longi- 

 tudes) of many objects having been settled from observation, nevertheless 

 these already settled points will not appear numerous ; as the process of 

 symbolizing proceeds, they will be found on the 1440 sheets of Form No. 3 

 requisite for drawing out the catalogue, few and far between ; and in order to 

 increase them, the use of the micrometer, or of a meridional instrument, will 

 be essential. There are three methods by which these points may be fixed. 

 First, by differences of right ascension and declination between the preceding 

 or following, and upper or lower limbs of the moon and the object, the lati- 

 tude and longitude of which is to be determined. This method was em- 

 ployed by M. Bouvard at the Eoyal Observatory of Paris in 1808 to 1810. 

 From a series of 124 such differences in each direction, M. Nicollet deter- 

 mined the selenographical latitude and longitude of the crater Manilius, and 

 also the amount of the moon's libration. Second, by measures taken with 

 the micrometer between the apparent east and west and north or south limbs 



* See Julius Schmidt's communication to the ' Astronomische Nachrichten,' translated 

 by Lynn, on page 299. 



