19II] OF RAINBOWS 179 



Double Bows — diameters must be 84° and 100° — again 

 from laws of refraction — colours: inner, red outside; outer, 

 red inside — i.e. reds come together. 



Wanted to see more rainbows on Barrier. In this connection 

 a good rainbow was seen to N.W. in February from winter 

 quarters. Reports should note colours and relative width of 

 bands of colour. 



Iridescent Clouds. — Not yet understood; observations re- 

 quired, especially angular distance from the sun. 



Auroras. — Clearly most frequent and intense in years of 

 maximum sun spots; this argues connection with the sun. 



Points noticed requiring confirmation : 



Arch: centre of arch in magnetic meridian. 



Shafts: take direction of dipping needle. 



Bands and Curtains with convolutions — not understood. 



Corona : shafts meeting to form. 



Notes required on movement and direction of movement — 

 colours seen — supposed red and possibly green rays preceding 

 or accompanying movement. Auroras are sometimes accom- 

 panied by magnetic storms, but not always, and vice versa — 

 in general significant signs of some connection — possible com- 

 mon dependents on a third factor. The phenomenon further 

 connects itself in form with lines of magnetic force about the 

 earth. 



(Curious apparent connection between spectrum of aurora 

 and that of a heavy gas, ' argon.' May be coincidence.) 



Two theories enunciated : 



Arrhenius. — Bombardments of minute charged particles 

 from the sun gathered into the magnetic field of the earth. 



Birkeland. — Bombardment of free negative electrons gath- 

 ered into the magnetic field of the earth. 



It is experimentally shown that minute drops of water are 

 deflected by light. 



It is experimentally shown that ions are given ofif by dried 

 calcium, which the sun contains. 



Professor Stormer has collected much material showing con- 

 nection of the phenomenon with lines of magnetic force. 



Thursday, May 4. — From the small height of Wind Vane 

 Hill (64 feet) it was impossible to say if the ice in the Strait 

 had been out after yesterday's wind. The sea was frozen, but 



