PROCEEDINGS OF THE CANADIAN INSTITUTE. 123 



The Cause of the Accumulation of Magnetic Storms when the Earth is Near 

 THE Equinoxes. By Andrew Elvins. 



{Read yth February^ igoj.) 



In a paper read before this Institute about a year ago on sun-spots and the 

 phenomena which seem to be connected with them, I expressed the idea that sun- 

 spots, aurorse, and magnetic storms are caused by matter forming in space, and 

 passing sunward in orbits more or less elliptical, which, when they cross the earth's 

 orbit, produce auroroj and magnetic storms, pass on sunward, and by planetary 

 perturbations and collisions fall in part on the sun and produce solar-disturbances. 

 Supposing the theory then advanced to be correct, I wish to show how it is the 

 fact that magnetic disturbances are more numerous at times when the earth is near 

 the equinoxes than at other times. 



The fact that disturbances are more numerous when the earth is at the equi- 

 noctial points, than at other parts of its orbit, shows it to be in some way connected 

 with the earth's annual revolution. 



Let us look for a moment at this motion. The sun is at the centre of the path 

 in which the earth moves. We call the plane in which the earth 

 moves the plane of the ecliptic. Whilst the earth is making its 

 annual revolution, it is also rotating on its axis, and this axis is not 

 at right angles to the plane of the ecliptic but about 24° from it. 



If the poles were at right angles to the plane of the earth's path, each of the 

 poles would be equally exposed to matter coming sunward from without in each 

 month in the year (and as the planets move near this plane, and reach outward 

 into space, their action on incoming cosmic matter will cause the larger part of it 

 to move in this plane also ; cosmic matter will be more abundant near the ecliptic 

 than elsewhere) ; the earth in passing through it will have one pole more exposed 

 to this matter during one half of its orbit, and the other pole most exposed during 

 the other half. But at the equinoxes both poles will be equally exposed, and at 

 any given point, except, perhaps, near the equator, the plus of cosmic matter 

 which produces magnetic disturbances will fall on the outside hemisphere of the 

 earth when (7 is near the equinoxes. 



On this theory cosmic matter passing by the earth going sunward is the cause 

 of auroras and magnetic disturbances ; the plus of such matter caused by the action 

 of Jupiter and Saturn, on incoming cosmic matter, is encountered by the earth 

 when it passes us going sunward, and this is the cause of the long 11-year period. 

 The moon's revolution, combined with the earth's motion, is the cause of the 25- 

 day period, and the inclination of the earth's axis is the cause of the plus of dis- 

 turbances at the equinoxes. 



