166 KECORDS OF DISTURBANCES 



movements occurred between 6 p.m., G.M.T., on the 12th and 3 a.m., G.M.T., on the 13th (5 a.m. to 2 p.m. 

 on the 13th, Antarctic L.T.). They are thus subsequent to the movements shown in Plate XXXV, and 

 answered to a time when much of the Antarctic trace was bi-yond the limits of registration. During the 

 time covered by Plate XXXV the range at Kew was 18' in D and 75y in H, but later, during the two hours 

 10-12 p.m., G.M.T., on the 12th there was a range of 37' in D and 180y in H. During a portion of the 

 two hours specified the Antarctic D and H curves were off the sheet simultaneously ; the V trace, however, 

 was less disturbed then than at various other times. 



This is a conspicuous example of the disadvantages attending the use of high sensitiveness in the 

 Antarctic. 



76. Plate XXXVI shows disturbances in the Antarctic on December 13-14, 1903, corresponding to those 

 at the co-operating stations shown in Plates XX and XXI. At the co-operating stations there was a sudden 

 commencement, but it was not very clearly indicated in the H curves at Kew and Falmouth, and its 

 duration in the D curves at these two stations appeared less than in the H curves at Colaba and Mauritius. 

 The Antarctic curves also show a sudden movement, especially that for D. The trace for this element 

 shows a peak at 1 1.28 p.m., L.T. (0.21 p.m., G.M.T.), followed by a downward movement. During the first 

 two minutes of its occurrence the downward movement is slow, but it suddenly accelerates at 11.30 p.m., 

 L.T., and the movement down the sheet during the next minute represents a rise of 36' in D. This is 

 followed by a less rapid, but larger, movement in the opposite direction, which continued until 11.40 p.m., 

 L.T. (0.33 p.m., G.M.T.), and represented a fall of 77' in D. The second movement, it will be observed, 

 covers the time of the double oscillation seen at Kew and Falmouth. The first movement may possibly be 

 represented by some movements indistinctly shown in the Kew and Falmouth H curves prior to 0.29 p.m., 

 G.M.T. 



The Antarctic V trace shows also a distinct double movement, first up, then down the sheet. The 

 summit is distinctly shown at about 11.36 p.m., L.T. (0.29 p.m., G.M.T.). The movements are small, and 

 V was increasing when the first movement set in, thus it is difficult to assign an exact time for its 

 commencement; it occupied apparently not more than one or two minutes, and was most likely 

 synchronous with the rapid part of the commencing D movement. The second, or decreasing, movement 

 in V lasted four or five minutes. It was about 18y and about double the first movement. 



Plate XXXVI consists, it will be noticed, of two portions, separated by an interval of about 3 hours. 

 During this interval the D and H traces were both continuously beyond the limits of registration. The 

 H trace was, in fact, beyond the limits from 11 p.m., L.T., on the 13th until 9.30 a.m. on the 14th. The 

 mode of its reappearance, as shown in the end or right-hand portion of the plate, is such as to suggest that 

 the limit of registration answering to low values of the element was very much exceeded. The limit 

 answering to high values was also exceeded between 10 and 11 a.m., but only for about 12 minutes. 



The left-hand portion of the plate shows D executing considerable oscillations, with a general drift down 

 the sheet after midnight until 5 a.m., L.T., when the limit of registration was exceeded for a few minutes. 

 The total range during these five hours was 4 12'. The right-hand portion of the plate shows the D trace 

 reappearing after three hours' absence, and then alternately on and off the sheet until 10.30 a.m., L.T., 

 when a very rapid movement up the sheet (diminution of the element) took place. The complete width 

 of the sheet, answering to 4 52', was crossed in about 18 minutes. 



The final portion of Plate XXXVI answers to the end of the Antarctic sheet of December 13-14. The 

 following Antarctic sheet (not reproduced) shows further large disturbances lasting until about 6 p.m., L.T., 

 on the 14th. The most notable V change occurred during the afternoon of the 14th. It consisted of a 

 rise of about 240y between 1.10 and 1.50 p.m., L.T. D increased 4 8' between 1.5 and 3.5 p.m., L.T., and 

 then diminished 3 57' between 3.5 and 5.15 p.m., L.T. A rough estimate of the sum of the D movements, 

 taken irrespective of sign, which were recorded between 10.30 a.m. and 5.15 p.m., L.T., on December 14, 

 proved to amount to no less than 25. 



On October 31 and the early morning of November 1, 1903, there occurred the largest magnetic 

 storm recorded at Kew during several years, but of this no record was obtained in the Antarctic, as the 

 magnetographs were not in action on October 31, nor on the subsequent day until the late afternoon. 



77. The seven Plates XXXVII to XLIII contain copies of portions of a number of Antarctic curves 



