ASTRONOMY AND METEOROLOGY. 309 



passing a diaphragm with a slit in it between the lens and the 

 mirror. A better effect is thus obtained than by the usual method 

 of placing it near the plate-holder. The lens, which was made 

 by Messrs. Clark and Sons, is not achromatic, as its slight curvature 

 rendered this unnecessary. It was corrected for spherical aber- 

 ration by means of an artificial star, produced by a soda flame, 

 and a collimator, of an aperture somewhat greater than that of 

 the lens. 







SPECTRUM OF THE SOLAR ATMOSPHERE. 



M. Rayet, in a note to the " Comptes Rendus " of Aug. 1, 1870, 

 shows that particular conditions are needed in order that vapors 

 of iron in the atmosphere should only give 5 lines. He finds that 

 it is possible to see 22 luminous lines of various substances in the 

 spectrum of the solar atmosphere, and gives the wave-length of 

 some lately observed lines. 



SOLAR SPOTS. 



M. R. Wolf, of Zurich, has just published the resume of his ob- 

 servations on the solar spots made since 18G4. The minimum 

 occurs in 1867, and agrees with the period of 11 1-9 years, found 

 by Sabine and himself. Designating the relative frequency of the 

 spots by r, M. Wolf expresses the variations of the magnetic 

 declination at Christiania by the formula r 0.0413'r -j- 4.921', 

 which does not, however, completely agree with observation. 

 Moniteur Scientifique. 



THE ROYAL ASTRONOMICAL SOCIETY. 



March 11, Mr. Proctor read a paper entitled " Notes on the 

 Corona and the Zodiacal Light," with suggestions respecting the 

 modes of observation to be applied to the eclipse of next Decem- 

 ber. He remarked that if we have in reality sufficient evidence 

 to determine whether the corona is or is not a solar appendage, it 

 would be a misfortune, and in a sense discreditable, to science, 

 were the short time at the disposal of observers wasted in futile 

 observations directed to settle a point determinable beforehand. 

 He then expressed his conviction that the corona cannot be a ter- 

 restrial phenomenon. He pointed out that the very blackness of 

 the moon as compared with the corona showed that the coronal 

 light is behind the moon. The moon is, in fact, projected on the 

 corona as a background, he urged, whereas the theory that the 

 light is due to atmospheric glare requires that the corona should 

 be a foreground. But passing over this argument, which is lia- 

 ble to the fatal objection of being too simple, he proceeded 

 to inquire whether air which lies between the observer and the 

 corona is in reality illuminated. He showed that all round the 

 sun, for a distance of many degrees, there should be perfect dark- 



