MAGNETIC DISTURBANCES. 133 



that I acquainted the Academy at Berlin with the peculiar 4 

 nature of these extraordinary disturbances, and even invited 

 my friends to visit me at predetermined hours, at which I 

 hoped they might have an opportunity of witnessing this 

 phenomenon ; and, in general, I was not deceived in my an- 

 ticipations.* Kupffer, during his travels in the Caucasus in 

 1829, and at a later period, Kreil, in the course of the valu- 

 able observations which he made at Prague, were both en- 

 abled to coniirm the recurrence of magnetic storms at the 

 same hours. f 



The observations which I was enabled to make during the 

 year 180G 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 sta- 

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

 through the accumulation of a rich harvest of materials, 

 which have been most skillfully elaborated by General Sa- 

 bine. In the results of both hemispheres this talented observ- 

 er has separated magnetic disturbances, according to diurnal 

 and nocturnal 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,f and the same was the 

 case in the oldest observations at Berlin ; exactly the re- 

 verse of what w r as found in from 2600 to 3000 disturbances 



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

 published in PoggendorfFs Annalen der Physik, bd. xv. (April, 1829), 

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

 ations, which I made conjointly with Oltmanns, had the advantage 

 that at that period (180G and 1807) none of a similar kind had been 

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

 maxima and minima ; they also showed how remarkable magnetic 

 storms could be recognized, 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 mete- 

 orological relations has hitherto been recognized as the inducing cause 

 of the phenomena." The earliest record of a certain periodicity of 

 extraordinary 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. 



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

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

 days consecutively." 



% Sabine, Unusual Disturb., vol. i., pt. i., p. xxi. ; and Younghus- 

 band, On Periodical Laws in the larger Magnetic Disturbances, in the 

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



