Sentence:  But both from experiment and from our first principles, which remain to be more especially explained in our theory of the <WSD>tellurian</WSD> vortex, it is evident, that the north magnetic pole moves round the north <WSD>tellurian</WSD> pole, sooner than the south magnetic pole moves round the south <WSD>tellurian</WSD>; and this is because the distance of the two from the centre of the vortex is not similar, and because also of the spiral contorsion of the vortex. 
Meaning of the word marked with <WSD> tags:  Of or relating to the earth;  inhabiting planet Earth as opposed to other planets. (from mid 19th c.)