ON MAPPING THE SURFACE OF THE MOON. 3 



which the Committee request may be renewed, is uot available for supplj-ing 

 an instrument suitable for this puiiDose, as it is necessarilj' expended in 

 earryiug on tlie work of mapping, registration, &c. Nevertheless' the Com- 

 mittee hope that aid may be afforded by which this desii-able object may be 

 attained, as, by the use of such an instrument, an authority will be given to 

 the work of a kind which it would not other^dse possess. 



Alleged Change on the Moon's Surface. — On the 27th of November 

 186G, the Committee received a communication from Herr Schmidt, Di- 

 rector of the Observatory at Athens, announcing that a remarkable change 

 had taken place in the crater " Linne." The importance of this communi- 

 cation was at once apparent, as bearing in one direction on on interesting 

 question on lunar physics, and in another on the labom-s of tlie Committee. 

 Two years ago the Committee urged the necessity of so registering an object 

 that it might ever after, in all time, be sufficiently identified by all future 

 observers (Eeport, 1865, p. 294). Tlie announcement of Schmidt suggests a 

 modification ; for if a change sufficiently extensive should take place in any 

 object, the condition of which had been definitely settled by more than one 

 observer, it might be difficult to identify it as the same object, but the value 

 of the determination of its former condition would be increased, both deter- 

 minations being equally good. In the particular case of " Linne," it is only 

 in the latter part of 1866, and up to September 1867, that its real state may 

 be regarded as settled upon the testimony of numerous observers, whose 

 observations fairly agree among themselves. With regard to its former 

 state there is some doubt, in consequence of real or supposed inexactitude in 

 previous observations, from which it is difficult to arrive at a conclusion; 

 an earlier observation agreeing (in the opinion of most astronomers) with 

 its present appearance, while others of a later date are ii-reconcileablc with 

 it. In the present state of Selenography a record of its real condition at any 

 particular epoch is so obviously important that nearly the whole of the obser- 

 vations, both early and recent, that have come into the possession of the 

 Committee, are given in an appendix ; those not inserted are mere repetitions 

 of similar features. 



Herr Tempel's opinion of the round white spots on the moon's surface 

 (analogous to the appearance which Linne now presents) being of interest 

 for the existence of a chemicalhf warm activiti/ (Astronomische Nachrichten, 

 No. 1655, translated by W. T. Lynn, B.A., F.R.A.S., Astronomical Eegister, 

 No. 58, p. 219), demands attention. These spots, which are very numerous, 

 have usually been considered as ground-markings, but as Linne, in 1788, 

 and in 1866-67, presented a similar appearance, they will in future com- 

 mand more attention. 



During the past year the Committee have issued three Circulars : — No. I. 

 announcing the change in Linne ; No. II. Tables of the periods of visibility 

 of those portions of the surface near the moon's limb periodically concealed 

 by changes of libration ; and No. III. a resimn' of the results of observations 

 of Linne up to June 1867. A portion of this Cii'cular, with additional obser- 

 vations,- will be foimd in the Appendix. 



APPENDIX. 



Linn£. — Observations, eaelt and recent. 

 Linne is marked A in Lohrmanns Section IV. 



1 (a). Scheuter's observation, 1788. — " Nov. 5, 4'' 30'" to 8'' (Seleno- 

 topographische Fragmente, vol. i. p. 181). Diesechste Bergader kommt von 



• b2 



