1867.] Astronomy. 229 



have been less satisfactory than that of the August meteors effected 

 by Mr. A. Herschel. The sudden cessation of the display pre- 

 vented Mr. Herschel from attending to this point as he had intended 

 to do. Mr. Browning notes the probable appearance of a yellow 

 line in the spectra of several meteors, and of a line of green light 

 in the spectra of two meteors. 



Herr Schmidt's observation of the disappearance of the lunar 

 crater Linnd has received the attention it deserved. It seems to 

 be now placed beyond a doubt that a change has occurred at this 

 point of the moon's surface. Observers have often before had 

 occasion to suspect the occurrence of variation, but hitherto there 

 has been no observation so satisfactory as that made by Herr 

 Schmidt. We not only have his evidence that he has been familiar 

 with the mountain since 1841, but the drawings of Lohrmann 

 (1823), who described the crater as very deep. It must be ex- 

 plained that, for the satisfactory observation of a lunar crater, the 

 sun must have only a small elevation at that point of the moon's 

 surface, — in other words, we must observe the spot when near the 

 terminator. The crater now obscured, used to become visible as a 

 crater — that is, in shadow — when the sun's elevation was less than 

 5°. " Noiv" says Schmidt, " in lower altitudes of the sun, and 

 close on the phase, not only is a crater never visible, but there 

 appears, in a good light, and with magnifying powers of from 300 

 to 600 at most, a very delicate hill of 300 toises (about 1,920 

 English feet) in diameter, and 5 to 6 toises (about 35 feet) in 

 height." As a light spot Linne continues always visible; as a 

 crater it has entirely disappeared. From views taken lately by 

 some of our most careful observers, it would seem as if the cloud, 

 or haze, which appears to have hung over the crater, were being 

 now gradually dissipated. Probably, in the course of a lunation 

 or two, we shall have more definite intelligence. It will be well to 

 avoid speculation until observation has done its work. In the 

 meantime, we have additional evidence, if any were needed, of the 

 value and necessity of the lunar-mapping now in progress. 



We have again to refer to the variable T Coronae, whose 

 sudden outbreak formed one of the most noteworthy astronomical 

 events of the year 1866. The whole significance of this occurrence 

 depended on the question whether it were really a sudden outbreak, 

 or whether the star arrived at its maximum of brilliancy by a 

 gradual process of change. Mr. Hind, therefore, did well in 

 calling the attention of astronomers to the reported observations of 

 Mr. Barker, of Canada, who stated that he had seen the star on 

 the 4th of May — eight days before the observation of Mr. Baxen- 

 dell ; and (subsequently) that he had noted a gradual increase of 

 brilliancy up to May 12th. Herr Schmidt, on the other hand, 

 expressed with confidence his opinion that the star was not con- 



