PROGRESS OF METEOROLOGY IN 188!». 259 



(7) Often, waves of light run along the arches; eastward and west- 

 ward motion of the waves were equally frequent. 



(8) The author rejects the classification of auroral forms given by 

 Weyprecht, and distinguishes only two different forms of auroral light, 

 viz, zones, or horizontal layers of light, and arches, composed of rays 

 parallel to the dipping needle. The arches are of four varieties : (1) 

 arch, or a regular baud; (2) baud or drapery; (3) spiral ; (4) pseudo- 

 arch. 



(9) The auroral light is of two kinds: (1) the yellow light, entirely 

 monochromatic ; (2) the crimson or violet light. 



(10) No sound was ever heard from the aurora. 



(11) The aurora wa's never seen to descend below the mountains or 

 lower clouds. Only two or three times it is possible that the light was 

 seen below the upper clouds. Direct measures of the i)arallaxfrom the 

 end of a short base (573 meters) gave an average height of 55.1 kilom- 

 eters, and by several other methods about 2 kilometers was found to 

 be the probable mean height of the aurora. 



(12) No annual variation could be discovi red. 



A daily variation having its maximum at 3 p. m., and miuimum at 8 

 A. :m., local time, was computed. {Xatiire^ xxxviii, i>. Sf.) 



XL— SCINTILLATION; LIGHT AND COLOR OF THE SKY; TWILIGHT 



GLOWS, ETC. 



Scintillation of the stars. — Dr. J. M. Pernter has conducted some scin- 

 tillometer observations upon the Sonnblick (elevation 3,100 meters), in 

 order to determine whether there is greater steadiness at high than at 

 low levels. Two of Exner's scintillometers were used in the work, and 

 simultaneous observations were made on two nights at the summit and 

 at Eauris (900 meters). The result of these comparisons showed that 

 the scintillation was noticeably greater at tlie summit than at Kauris. 

 Dr. Pernter properly draws the conclusion that scintillation does not, in 

 all cases and exclusively, take place in the lower air layers, and that 

 many cases occur in which the air above 3,100 meters elevation is more 

 ])roductive of scintillation than that at lower levels. Pernter further 

 concludes that little or nothing is gained in steadiness by building ob- 

 servatories at high elevations ; but Exuer considers the observations too 

 few to warrant this generalization and considers that it is simply proved 

 that the Sonnblick is not particularly suitable for an astronomical ob- 

 servatory. {Meteorologische Zeitschrift, 18S9, vi, p. 30.) 



Spectro-Tphotometry. — M. Crova has presented a i)aper to the Paris 

 Academy of Sciences on the analysis of the light diffused by the sky. 

 Ue made observations on the to|) of Mont Veiitoux with a modified 

 form of his spectro-photometer, which could be directed to any part of 

 the sky. 



The curves for zenithal light show a predominance of the more re- 



