QQQ Professor W. G. Adams [June 3, 



time lias arrived wlien there sliould be photographic registration of 

 the magnetic elements at such an important observatory as the Cape 

 of Good Hope, especially when the French Government has decided, 

 within the last few weeks, to establish a magnetic observatory at Cape 

 Horn. With observatories at Melbourne, at Cape Horn, and at the 

 Cape of Good Hope the southern hemisphere would be well supplied ; 

 and probably the Kussian Government would then soon establish an 

 observatory in the east of Siberia, where it is very desirable that a 

 magnetic observatory should be established. 



Now we can readily show by experiment the way in which the 

 magnetic instruments may be disturbed in a magnetic observatory by 

 the alteration of the strength of a magnet. Taking magnetic needles 

 to represent the declination needle, the inclination needle, and the 

 bifilar or horizontal force needle, we may place an electro-magnet in 

 a given position with regard to them, and by altering the strength of 

 that electro-magnet may cause these needles to trace out disturbances 

 of a very decided character. 



I have as yet been sj^eaking of only moderate disturbances, but now 

 let us come to some of the larger ones ; and I have had the oppor- 

 tunity through the kindness of the Kew Committee and the observers 

 at the various observatories mentioned, of studying the curves for the 

 August magnetic storm, which began at 10.20 a.m., Greenwich time, 

 on August 11th, and for convenience may be divided into three 

 storms, one lasting from 10.20 on the 11th to 1 a.m. on the 12th ; a 

 second from 11 .30 a.m. on the 12th to 7 .20 on the 13th, and the third 

 from 11.50 a.m. on the 13th to 7 to 8 a.m. on the 14th of August. I 

 have prepared a large sheet on which these curves have been copied 

 as accurately as possible for the first of these storms on the 11th (see 

 Plate 3). For this storm I have also the curves from Toronto and 

 from Zi-Ka-Wei. The first storm began on August 11th at the same 

 instant at all the stations. There is a decided similarity, especially in 

 the horizontal force curves, throughout the first part of this storm, and 

 certain points in it stand out prominently. At Kew the beginning of the 

 storm is not actually recorded, because the sheets of prepared paper 

 on the time cylinders were changed precisely at 10.20 a.m., when the 

 storm was beginning. The deflections are alike at Lisbon, Kew, 

 Vienna, St. Petersburg, and, after the very first sudden deflection, at 

 Toronto also. The greatest effect is produced at St. Petersburg ; the 

 similarity between the large disturbances at Vienna and at Toronto, in 

 Canada, places differing about 6^ hours in time, is remarkable. 

 About 11.45, 1 p.M, and 2.40 p.m. there are very remarkable points 

 of agreement. 



From about 4 . 30 p.m. to 8 p.m., Greenwich time, i. e. from about 

 11 a.m. to 2.30 P.M., Toronto time, the deflections are opposed at 

 Toronto and at Vienna or Kew. This would rather point to solar 

 action as the cause of disturbance. In this case the Kew curve is 

 not so much deflected as the Vienna curve, because the horizontal 

 needle at Kew is not nearly so sensitive as at Vienna, and the relative 



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