ON MAPPING THE SURFACE OF THE MOON. 287 



[Form No. 1.] British Association for the Advancement of Science. 



Observatory, 



General Observations of the Moon, made at the 

 By 

 Telescope 



Eye Piece 



This Form is intended to be bound in volumes for use in observatories. It 

 contains the usual columns for registering the year, month, day and hour of 

 observation, a "wide column for the reception of the observations themselves, 

 and two additional columns, one for the registration of the brightness of objects, 

 the other for receiving a symbol of reference on which a word or two in ex- 

 planation may be appropriate. 



Whatever object may be the subject of observation, either physical or 

 micrometrical, as soon after the observations as may be convenient, the pro- 

 per symbol of reference which is described in Form No. 2 is to be inserted in 

 the last column against the name or description of the object observed ; and 

 as Form No. 1 is intended as a chronological record of observations of all 

 kinds, the entries in this column will indicate the proper sheets of Form No. 3, 

 in which the data obtained by observation are to be entered. Employing a 

 commercial simile, Form No. 1 is the day book, Form No. 3 the ledger, and 

 Form No. 2 the directions for posting. 



A vast amount of detail having reference to the moon's surface has been 

 accumulating since the time of Hevelius, but up to the present period a 

 systematic arrangement of the objects discoverable on the surface has not 

 been attempted ; for although Beer and Madler in their " Der Mond " have 

 arranged the descriptive part of their work in quadrants, commencing with 

 the north-west and ending with the south-west, it embraces only the most 

 conspicuous objects ; numerous features, some even of large extent, are 

 entirely passed over, and indeed those which have been noticed by Beer and 

 Madler form a very small portion of the objects that may be detected with a 

 telescope even of small aperture, or an object glass of two or three inches 

 diameter. It is also not a very easy matter to arrange objects on the moon's 

 surface, inasmuch as they are unlike those celestial objects which have been 

 arranged in catalogues. The fixed stars, double stars, variable stars, and 

 nebulae find a natural arrangement in the order of right ascension ; not so the 

 objects on the moon's surface ; it is true they are invariably situated with 

 regard to the central meridian of mean libration, but to arrange them in the 

 order of selenographical longitude east and west of the central meridian, it 

 is necessary that the position of each should be rigorously determined, a 

 work that still remains to be done, and it may be many years before it can 

 be accomplished. 



In order to meet this desideratum, the Committee have drawn up and 

 issued the following Form (No. 2) for facilitating the arrangement of a cata- 

 logue by means of symbols ; and in accordance with it more than 1000 

 objects are now symbolized and entered in Form No. 3. 



