of Terrestrial Magnetism. 103 



how these phenomena would be found to comport themselves in 

 succeeding years. Supposing the continuance of the same cycle 

 in the variations both of the solar spots and of the magnetic 

 disturbances which had been traced up to 1851, the next epoch 

 of minimum might be looked for in 1853 or 1854. The British 

 Colonial observatories having terminated, I availed myself, for 

 the purpose of this investigation, of the means afforded by the 

 hourly magnetic observations made by direction of the Russian 

 Government at Pekin, from 1852 to 1855 inclusive. The obser- 

 vations themselves are published by M. Kupffer in the 'Annales 

 de PObservatoire central de Russie/ and are discussed by my- 

 self in the Introduction to the second volume of the ' St. Helena 

 Observations/ published in 1860, pp. cxxxv. to cxliv. The 

 ratios of disturbance in the years 1852 to 1855, taking the 

 mean of the four years as the unit, were as follows : — 



1852 1-01 to 1 



1853 0-82 to 1 



1854 079 to 1 



1855 1-38 to 1, 



marking the epoch of minimum as having occurred in 1853-54. 

 By the aid of the Kew Observatory (which owes its existence 

 and support to the public spirit and liberality of the British 

 Association, and which in 1857, by a grant from the Royal 

 Society of a portion of the £1000 annually entrusted to their 

 disposal by Her Majesty's Government, was enabled to com- 

 plete an equipment of automatic instruments by which a con- 

 tinuous register of the variations of the three magnetic elements 

 is maintained), we are able to trace the succeeding epoch of 

 maximum : the aggregate magnetic disturbance was of nearly 

 equal amount in 1858, 1859, and 1860 ; whilst in the follow- 

 ing year (1861) a very considerable decrease showed that the 

 maximum had passed and had taken place at the time antici- 

 pated, viz. in 1859, as the middle year of the three years of 

 highest ratios. And here it may be desirable to remark that 



presented to the Royal Society in January 1851, and printed in the Philo- 

 sophical Transactions for 1851, Art. V. 



The existence of a periodical variation in the magnetic disturbances, 

 coinciding in period and epoch with the variation in frequency and magni- 

 tude of the solar spots announced by M. Schwabe, was communicated to the 

 Royal Society (as stated in the text) in March 1852, and was printed in 

 the Philosophical Transactions for 1852, Art. VIII. 



The inequality or variation in the mean diurnal range, in different years 

 and in different seasons, of the declination and horizontal force from 1841 

 to 1848 inclusive, and of the vertical force, inclination, and total force from 

 1842 to 1848 inclusive, was published in the same month as the last-named 

 communication to the Royal Society, viz. March 1852, in vol. ii. of the 

 ' Magnetical Observations at Hobarton in Van Diemen Island.' 



