1869.] Astronomy. 263 



Mr. Biit discusses at considerable length the subject of the 

 Lunar Crater Linne. From the drawings made at different times 

 by Messrs. Huggins, Noble, and Tacchini, he has estimated the 

 dimensions of the cone, crater, and orifice of this interesting object. 

 He remarks that these estimates must be received as approximations 

 only, serving rather as a guide to observers than as being expres- 

 sions of the exact state of Linne at the present epoch. Those who 

 see in the varying appearance of Linne a proof of the activity of 

 lunar volcanoes in the present day, should study the researches of 

 Mr. Birt on the probable configuration of the crater. 



Mr. Kincaid suggests an ingenious mode of constructing an 

 automatic transit instrument. The apparatus consists of a plane 

 mirror and a burning-glass, to be adjusted in such a manner that, 

 at the instant the sun reaches the meridian, the rays ignite a thread 

 which burns without smoke or residue ; this releases a detent, and 

 a motion is thereby given to the hands of the clock, bringing it to 

 the correct local mean time. There is a supplementary arrange- 

 ment by which if the thread should not ignite, in consequence of a 

 j)assing cloud, at the instant of the transit of the first limb, the 

 subsequent ignition of the thread will not affect the clock. 



Mr. Lockyer, in a note on Mr. Huggins's paper " On a possible 

 Method of viewing Eed Flames without an Eclipse," writes to show 

 that he was not aided by the eclipse observations in seeking for the 

 prominence-spectrum. Unless Mr, Lockyer claims credit for the 

 discovery of the gaseity of the prominences, apart from the credit 

 due to him for his share in the discovery that their spectrum can be 

 seen without an eclipse, we cannot see how Mr. Huggins's mistake 

 (assuming it to be such) at all afl'ects the proper apportionment of 

 recognition in the matter of recent solar discoveries. The eclipse 

 observers clearly deserve all the credit due to the first-mentioned 

 discovery, which had been fully discussed in England for two 

 months before Mr. Lockyer examined the prominence-spectra. It 

 is impossible to undiscover the discovered. On the other hand, no 

 one has disputed the claim of Janssen and Lockyer to the discovery 

 that the prominence-spectra can be seen without an eclipse. 



Professor Brayley supplies an interesting paper on the relation 

 of the luminous prominences to the faculse of the sun. He shows 

 that there is strong reason for supposing the faculfB and pro- 

 minences to be identical, or at least that the latter are the superior 

 terminations of the former. 



Some very singular facts connected with the mean distances of 

 the asteroids and the commensurability of their periods with that 

 of Jupiter are pointed out by Professor Kirkwood. He shows that 

 wherever there is a wider gap than usual between the asteroids 

 (considered in the order of their distances from the sun), that gap 

 invariably corresponds with such values of the mean distance as 



T 2 



