162 RECORDS OF DISTURBANCES 



and Falmouth it was of a very trifling character, the range being under 6' in D and under 20y in H. In 

 the Antarctic the visible ranges, on the other hand, are 2 13' in D and 80y in H, and to all appearance 

 the D range at least was considerably larger. 



67. Plate XXV shows the disturbance in the Antarctic on November 24, 1902, corresponding to the 

 disturbance at Christchurch, shown in the lowest curve of Plate XV. This disturbance, though of 

 considerable size, had no very outstanding features either in the Antarctic or elsewhere. It occurred at a 

 time when there was a good deal of general disturbance, and the day was not very exceptional as 

 compared to adjacent days. The D curve, it will be seen, crossed from one edge of the sheet to the other 

 representing 4 50' and trace was lost at both sides. The range in D is, however, partly due to the 

 regular diurnal variation, which doubtless contributed considerably to the movement shown between noon 

 and 5 p.m. (L.T.). The H curve was off the sheet most of the time from noon to 4.30 p.m. (L.T.) on the 

 24th and the range probably largely exceeded that actually shown, 149y. 



The sensitiveness of the V magnet was less than half of what it possessed on November 7. The 

 movement shown on the trace represents about 171y, but a portion of this is due to temperature. 

 Between 11.30 a.m. (L.T.) on the 24th, when the minimum appears on the V trace, and 9 p.m. (L.T.) on 

 the 24th, when the maximum appears, temperature fell - 4 C. Allowing for this change of temperature, 

 the range is reduced to 154y. 



The identification of the D and H curves during the early part of the time covered by Plate XXV 

 presented some difficulties. It answers to the earlier part of the photographic sheet for the day 

 November 24-25 (L.T.). The interval between the putting on of this sheet and the taking off the previous 

 one was unusually long, exceeding an hour. The disturbances during the early part of the 24th covered 

 by the preceding sheet were very large, the to-and-fro oscillations in both D and II, if not so large as later 

 in the day, being more numerous and rapid. At the time when the sheet was taken off, the D trace had 

 been off the sheet for over an hour, while the H trace, after being repeatedly beyond both limits of 

 registration, was near the centre of the sheet. 



On the sheet for November 24-25 the first absolutely clear discrimination between the D and H traces 

 is afforded by the fact that the trace marked D did not become invisible at 5 p.m. This enables one to 

 identify the trace marked D as certainly Declination back to before 2 p.m. Prior to that one had to be 

 guided by the appearance of the traces, and on that particular day there was no very marked difference as 

 regards thickness of trace or definition. As to whether the small portion of curve which just came on the 

 sheet at about 0.20 p.m. (L.T.) represented D or H it was impossible to say. 



68. Plate XXVI shows disturbances in the Antarctic on April 6, 1903, the same date as those of 

 Plate XVI. 



Plate XXVI represents two portions of curves, the first extending from midnight on April 5 to 

 4.15 a.m. (L.T.) on the 6th, the second from 9.20 a.m. to 3.10 p.m. on the 6th. The intermediate portion 

 of curve was fairly quiet, and was omitted to bring the whole within the compass of one plate. The 

 disturbances in the earlier portion of curve have a range of 63' in D, 112y in H, and about 55y in V (the 

 temperature effect in this instance is small). They answer to disturbances occurring from 10 to 6 hours 

 earlier than those represented on Plate XVI. At Kew, the largest of these movements is represented by a 

 bay on the H curve, the element first rising, and then falling about 30y. This answered in time, at least 

 very approximately, to the movement shown on the Antarctic H curve between 3 and 4 a.m., L.T., but 

 was of only about one-third the amplitude. The second portion of curve in Plate XXVI answers to the 

 earlier portion of Plate XVI. What answers to the sudden commencing movement from 11.25 to 11.29 p.m., 

 G.M.T., at Falmouth and the other co-operating stations, is apparently the sudden movement up the sheet in 

 D and H, and movement down the sheet in V, shown in Plate XXVI as commencing at 10.32 a.m., L.T., 

 and lasting 4 minutes. But while the commencing movement at the co-operating stations was much more 

 prominent than the movements immediately following it, the reverse is true of the Antarctic, where the 

 commencing movement was immediately followed by an equally rapid and considerably larger movement 

 in the opposite direction. Towards the end of the second movement the rapidity of change diminished 

 notably in D and V. What happened in the case of H is uncertain, as the trace went off the sheet, but 

 the movement terminated earlier than was the case in V or D. The double movement in the H trace has 



