Blasius.I ^14 [Jan.Ki, 



traneous to the atmosphere. Prof. Young in Genf finds it in cosmic 

 dust ; Easterby ascribes the cause to chemical changes in the sun ; others 

 ascribe it to the influence of the aurora borealis or to the zodiacal light. 

 Lockyer considered that the volcanic ashes thrown into the air by the 

 eruptions of the Krakatoa, in August, 1883, is the true <'ause ; but I sup- 

 pose he has changed his views by this time, as the phenomenon reap- 

 peared in 1884 without the recurrence of any eruption. 



I will not enter into a criticism of these different views, but the general 

 impression is that the phenomenon remains as much a puzzle as ever. 

 This is perhaps not surprising, for so long as meteorologists continue to 

 hold to the old theory, that the movements and changes of the air in the 

 Temperate zone are of a cyclonic nature, so long they will be unable to 

 satisfactorily explain most meteorological phenomena, and the brilliant 

 sun-glows only add another to the list of failures. 



Seen from a standpoint I believe I have found by a study of nature to 

 be the true one, meteorological phenomena appear to the observer in a 

 natural undistorted state, and they are easily understood and explained. 

 The sun-glows and the ordinary sunset brilliancies, are caused by the 

 same forces, but under different meteorological conditions, which cannot 

 be understood so readily, when seen from the standpoint of the old 

 cyclonic theory. In the one, as well as in the other case, the color is pro- 

 duced by the refraction of the sun's rays in a stratum or sheet of moist 

 air. The surrounding stratum of moist air is often observed, especially 

 during the time the sun rises and sets ; therefore, the phenomena on a 

 small scale take place frequently. The more magnificent phenomenon 

 can only take place when, in the progress of the equatorial air current 

 northward, the warm, moist current comes between the observer and the 

 rising or setting sun. There is then going forward a displacement 

 of the cold, dry polar current or wave, by the moist warm equatorial cur- 

 rent or wave, the latter slanting obliquely up and over the polar air. 

 Where these currents meet they lie in the position of two wedges, the 

 polar current having the thin edge of its wedge toward the south, on the 

 surface. The warm, moist equatorial current has the thin end of its wedge 

 or sphenoid up and above the cold current toward the north ; its progress 

 is generally indicated by cirrus clouds, which in the further progress, 

 change into cirro-stratus. Ifthe observer is now situated in the polar cur- 

 rent, he will find the temperature low, the barometer high, and the air 

 comparatively dry, the wind coming from a northerly direction. Between 

 him and the rising or setting sun he would encounter, if he ascended in a 

 balloon, the equatorial current, a body of moist warm air in tlie shape of 

 a sphenoid, or wedge, or a prism. If there is a coincidence of the proper 

 conditions, especially if the plane of meeting of the two currents has 

 a tolerably steep inclination, the brilliant phenomenon as described will 

 show itself. 



For a more elaborate exposition of the relations of these equatorial and 

 polar currents under such circumstances, I must refer to my work : 



