MAGNETIC DISTURBANCES. 137 



tions. 78 Kupffer, during his travels in the Caucasus in 1829, 

 and at a later period, Kreil, in the course of the valuable 

 observations which he made at Prague, were both enabled 

 to confirm the recurrence of magnetic storms at the same 

 hours. 73 



The observations which I was enabled to make during the 

 year 1806, at the equinoctial and solstitial periods, in refer- 

 ence to the extraordinary disturbances in the variation, have 

 become one of the most important acquisitions to the theory of 

 terrestrial magnetism, since the erection of magnetic stations 

 in the different British colonies (from 1838 to 1840), through 

 the accumulation of a rich harvest of materials, which have 

 been most skilfully elaborated by General Sabine. In the 

 results of both hemispheres this talented observer has sepa- 

 rated magnetic disturbances, according to diurnal and noc- 

 turnal hours, according to different seasons of the year, and 

 according to their deviations eastward or westward. At 

 Toronto and Hobarton the disturbances were twice as fre- 

 quent and strong by night as by day, 74 and the same was the 

 case in the oldest observations at Berlin ; exactly the reverse 

 of what was found in from 2600 to 3000 disturbances at 

 the Cape of Good Hope, and more especially at the island of 

 St. Helena, according to the elaborate investigation of Cap- 



72 This was at the end of September, 1806. This fact, which was 

 published in Poggendorflfs Annalen der Physilc, Bd. xv (April, 1829), 

 s. 330, was noticed in the following terms : " The older horary obser- 

 vations which I made conjointly with Oltmanns, had the advantage 

 that at that period (1806 and 1807), none of a similar kind had beeii 

 prosecuted either in France or in England. They gave the nocturnal 

 maxima and minima ; they also showed how remarkable magnetic 

 storms could be recognised, which it is often impossible to record, owing 

 to the intensity of the vibrations, and which occur for many nights 

 consecutively at the same time, although no influence of meteorological 

 relations has hitherto been recognised as the inducing cause of the 

 phenomena." The earliest record of a certain periodicity of extraordi- 

 nary disturbances was not, therefore, noticed for the first time in the 

 year 1839. Report of the Fifteenth Meeting of the British Association at 

 Cambridge, 1845, pt. ii, p. 12. 



73 Kupffer, Voyage au Mont Elbruz dans le Caucase, 1829, p. 108. 

 " Irregular deviations often recur at the same hour and for several days 

 consecutively." 



74 Sabine, Unusual Disturb, vol. i, pt. i, p. xxi, and Younghusband, 

 On Periodical Laws in the Larger Magnetic Disturbances, in the 

 Transact, for 1853, pt. i, p. 173. 



