TERRESTRIAL MAGNETISM. 85 



Declination at Toronto, St. Helena, and Hobarton. (Phil. 

 Trans. 1853.) 



18531854. Sabine's new proofs from the observations 

 at Toronto, Hobarton, St. Helena, and the Cape of Good 

 Hope (from 1841 to 1851), of the character of the annual 

 variation superimposed upon the mean diurnal variation of 

 the Declination, and of the correspondence of its semi- 

 annual epochs with those of the Sun's passage of the Equator. 

 (Toronto Observations, Yol. ii. p. xxii. ; and Proceedings of 

 the Royal Society of London, May 1854.) 



The preceding chronological enumeration of the advances 

 which have been made in our knowledge of terrestrial mag- 

 netism in the course of the last half-century (during which 

 I have myself uninterruptedly devoted the warmest interest 

 to the subject) shows that they have had a two-fold character. 

 The most considerable portion of these labours is that which 

 has been devoted to the observation of the manifestations 

 of the earth's magnetic activity, and to their variations 

 according to time and place ; the smaller portion has been 

 given to experiments, or to the calling forth of phenomena 

 promising to conduct us to a comprehension of the essential 

 nature of the activity so manifested. These two lines of 

 research, on the one hand, that of observation of the 

 manifestations of terrestrial magnetism (in direction and 

 force), and on the other, that of physical experimentation 

 on magnetic force in general, have acted and reacted on 

 each other, and have concurrently animated and carried 

 forward our knowledge of Nature. Observation alone, 

 independent of any hypothesis on the causal connection of 

 the phenomena, or on the as yet immeasurable and 



