NOTES TO BOOK XII. 71 



termination of that period arrived, a discussion was held 

 among the magneticians themselves, whether it was better 

 to continue the observations still, or to examine and com- 

 pare the vast mass of observations already collected, so as 

 to see to what results and improvements of methods they 

 pointed. This question was argued at the meeting of the 

 British Association at Cambridge in that year ; and the 

 conference ended in the magneticians requesting to have 

 the observations continued, at some of the observatories 

 for an indefinite period, at others, till the year 1848. In 

 the mean time the Antarctic expedition had brought back 

 a rich store of observations, fitted to disclose the magnetic 

 condition of those regions which it had explored. These 

 were discussed, and their results exhibited, in the Philo- 

 sophical Transactions for 1843, by Col. Sabine, who had 

 himself, at various periods, made magnetic observations 

 in the Arctic regions, and in several remote parts of 

 the globe, and had always been a zealous labourer in 

 this fruitful field. The general mass of the observations 

 was placed under the management of Professor Lloyd, of 

 Dublin, who has enriched the science of magnetism with 

 several valuable instruments and methods, and who, along 

 with Col. Sabine, made a magnetic survey of the British 

 Isles in 1835 and 1836. 



I do not dwell upon magnetic surveys of various 

 countries made by many excellent observers; as MM. Que- 

 telet, Forbes, Fox, Bache and others. 



The facts observed at each station were, the intensity 

 of the magnetic force ; the declination of the needle from 

 the meridian, sometimes called the variation ; and its 

 inclination to the horizon, or the dip ; or at least, some 

 elements equivalent to these. The values of these elements 



