1885.] 



215 



fBlasius 



" Storms ; Iheir nature, classification and ]a"ws, with the means of pre- 

 dicting them." (Porter & Coates, publishers.) Especially to Plate vii, 

 p. 76, where will be found diagrams representing the north-east storm in 

 its progress, i. e., the warm moist southern current replacing the cold, dry- 

 northern current. 



Let us now examine how these views agree with the actual state of the 

 atmosphere on October 26, 1884, when this phenomenon last appeared. 

 To this end I copy the record from the United States Signal Service 

 record : 



From this we see that the meteorological conditions of the atmosphere 

 coincided favorably to show the phenomena in question to an observer in 

 Philadelphia. High barometer, low temperature, clear weather, north 

 erly wind. At 3 p. m. the wind came from the south, then the tempera- 

 ture rose, the pressure decreased, and toward 7 p. m. Cir. Cum. appeared, 

 indicating that the equatorial warm moist air, flowed obliquely over the 

 polar current, and that it took a position between the observer in Phila- 

 delphia and the setting sun, and that the sun's rays of necessity went 

 through the sphenoid or prism of the body of moist warm air, and so pro- 

 duced the brilliancy as described. Prof. Clement Hess,* from Frauenfeld, 

 describes similar conditions in the atmosphere when the phenomenon 

 took place in November 3, 1883, at his place of observation. The day pre- 

 ceding, all Europe was under high pressure, then came cirrus and cirro- 

 stratus, with low pressure in their rear traveling eastward. Prof. Hess con- 

 siders this low pressure a forward moving cyclone. Seen from my stand- 

 point, it is the equatorial current lying in the form of a sphenoid above 

 the polar current. The sun's position in relation to the inclination of the 

 plane of meeting or the gradient, is evidently of much importance, and if 

 we had all the facts, the result would be mathematically determined. 



If now it is asked why the brilliant sun-glows should not be observed 

 every autumn, I think the answer is that it but infrequently happens 

 that at this season of the year, when the sun is in position to produce this 

 effect, the equatorial current reaches to sufficiently high altitudes. And, 

 it will be remembered, that both in 1883 and to a less degree in 1884, the 

 approach of winter was exceptionally late, the equatorial current remain- 

 ing much longer than usual in its summer position. 



» Zeitschrift der Ostreichischen Gesellschaft fUr Meteorologie, xviii Band,p.20. 



