PHYSICS: E. THOMSON 
3 
greatest auroral display seen in our latitudes for more than half a cen- 
tury. Telegraph lines from east to west could not be operated owing 
to arcing at the keys. The display as witnessed by me, was character- 
ized by colored streamers passing upward from all around towards the 
zenith from north, east, west and south. The coloring gave me the 
first clue to the true relations existing. In the north the sharply de- 
fined streamers beginning their appearance low in altitude with the 
usual greenish auroral hght, shot, or spread upward with changes of 
tint, finishing at their upper ends in a deep crimson. The light patches 
of the zenith crown went through the same succession of coloring con- 
stantly, each time ending in deep crimson. This fact suggested in the 
strongest way that in the crown one was observing bundles of streamers 
on end, but of the same character as all the other streamers in the 
field of view. Great masses or broad bands to the east and west though 
steady were colored likewise. These dense masses in the east and west 
were unquestionably due to the composite effect of great numbers of 
streamers superposed in the line of sight through great distances to 
east and west; the colors less pure blurred by distance and failure of 
exact superposition. Other observers at places far to east and west 
of my position might observe zenith crowns but composed of other 
streamers seen on end. A necessary consequence of the display pre- 
senting the same appearance to observers in many places far apart, 
up to hundreds of miles east and west, and through a zone north and 
south, is that the streamers everywhere were in reality vertical, or 
approximately so, to the earth's surface. In Chicago, a distance west 
of about eight hundred miles, this aurora was described in the same 
way, the appearances coinciding with my observations. The effects 
being so similar in places far apart, the only inference possible is the 
one stated, namely, nearly vertical streamers wherever seen. 
In this view observations upon subsequent auroras could be made 
more intelligently than before. But auroral displays of great magnitude 
are rare in our latitudes, especially such as are so far south as to cause 
a belt of streamers directly over the place of observation giving the 
zenith crown. While several highly instructive displays occurred mean- 
while, one on September 29, 1908, gave streamers converging from all 
directions joining the crown in the zenith which had the usual char- 
acteristics. My note of it says ^'The rapid procession of streamers 
and the waving curtains make this display quite exceptional; though far 
inferior to that of April, 1883.'' On August 26, of this year (1916) 
there occurred a display second only in my experience to that of April, 
1883, but without the remarkable coloring of the display of that year. 
