MAGNETIC DISTURBANCES AND AURORA. 



199 



August 13, 1903. 



10.0 p.m. Fairly brilliant display, consisting of 

 a complete arc, extending from N. to S., and two 

 streamers. The highest point of the arc was due 

 E., with an altitude of 15. At its E.S.E. point 

 it was distorted by a relatively more brilliant and 

 wider zone of light with a streamer rising out of 

 it to 30 altitude. An independent ray also rose 

 to 30 altitude to the S.E., but did not quite reach 

 to the arc. The breadth of the arc was between 

 2 and 3, the lower edge more defined than the 

 upper, but neither particularly definite. Very 

 rapid movement and very rapidly changing in 

 form. 



By 10.10 p.m. the arc had completely dis- 

 appeared and was replaced by streamers of 

 irregular altitude and interrupted in their lengths. 

 The streamers rose at various points where the arc 

 had been, the extremes being at E.N.E. and S. by 

 E. points, with two more in between. The altitude 

 of the highest was 40. This latter display was 

 also very rapidly changing. 



10.20 p.m. Diffused streamer from due N., 

 spreading out fan-like to about 30 altitude, but 

 one thin band from one side of the fan extending 

 across the sky to the W. 



10.45 p.m. No aurora visible. 



At 11.10 p.m. fine arc in S., extending from 

 N.W. magnetic to N.E. magnetic (17 S. of E. to 

 17 W. of S.), altitude of apex 25, and exactly in 

 magnetic Meridian. 



The N.E. (magnetic) extremity much the 

 brightest and formed of vertical rays, while N.W. 

 (magnetic) and centre were rather faint and about 

 4 in width. The whole display moved rapidly 

 towards zenith and at the N.E. (magnetic) formed 

 draped aurora of a greenish tint 



A few isolated rays in N., altitude 40. Shortly 

 after a bright draped curtain appeared a little to 

 E. of zenith, altitude 80, and arc became very 

 faint. 



At 11.20 p.m. only a few faint cloud-like 

 patches here and there were visible. 



After 9.40 p.m. numerous oscillations appeared 

 in the V trace. A little before 10.0 p.m. V began 

 to increase rapidly. The maximum was reached 

 about 10.18 p.m., the rise being most rapid during 

 the last 6 minutes. The total increase since 

 9.30 p.m. was about 70y. 



After 10.18 p.m. V remained nearly constant 

 during 20 minutes. 



There was a deep bay on the D curve from 

 about 9.50 to 10.40 p.m. A decrease of about 70' 

 was followed by an equal increase, the turning- 

 point answering to about 10.12 p.m. 



The H curve showed a somewhat similar bay, 

 but it appeared somewhat earlier in time. 



The H trace was, however, beyond the lower 

 limit of registration from about 9.45 to 10.25 p.m., 

 so that the turning-point was not shown. 



Between 11.0 and 11.30 p.m. the V trace showed 

 a sharp double oscillation, the amplitude in each 

 being about 25y. The sharpest turning-point, 

 which answered to a maximum of V, occurred at 

 about 11.14 p.m. 



The adjacent minima, which were also clearly 

 shown, were at about 11.9 and 11.25 p.m. 

 respectively. 



There were sharp peaks on the D and H curves 

 at about 11.10 p.m., D increasing 27' between 

 11.10 and 11.13 p.m. Another very rapid move- 

 ment occurred between 11.16 and 11.25 p.m., 

 when D fell about 57'. 



It will be observed that both after 10.0 p.m. and after 11.0 p.m., whilst there were notable magnetic 

 changes synchronous with the brightest phases of the aurora, these were not more notable than the 

 magnetic changes recorded after the auroral display had become faint. 



