of intensity in the dipping and horizontal needles , &c. 185 
on the different magnetical subjects wherein I have been en- 
gaged, he has kindly given such a direction to my thoughts, 
as materially to assist me in arriving at the conclusions I 
have drawn. 
P.S.That the magnetic pole moves in an orbit round the pole 
of the earth, was first conceived, I believe, by Mr. Derham, 
as appears from the Appendix to Philosophical Essays, in 
three parts, by R. Lovett, lay clerk of the cathedral church 
at Worcester, published in 37 66, which was put into my 
hands by a friend, on mentioning to him the theoretical views 
advanced in this paper. This Appendix contains a brief 
theory of the north magnetic pole adopted by him from a 
passage in Derham’s Physico-Theology, which I shall tran- 
scribe in Mr. Derham’s own words, who, after stating the 
various discoveries of Norman, Gellibrand, and others, 
proceeds to say ; “ To these discoveries, I hope the reader 
“ will excuse me if I add one of my own, which I deduced 
“ some years ago, from some magnetical experiments and 
“ observations I made ; which discovery I also acquainted 
“ our Royal Society with some time since, viz. that as the 
“ common horizontal needle is continually varying towards 
“ the east and west, so is the dipping needle varying up and 
“ down, towards or fromwards the zenith, with the magne- 
“ tick tendency describing indeed a circle round the pole of 
“ the world, as I conceive, or some other point ; so that if 
“ we could procure a needle so nicely made, as to point ex- 
“ actly according to its magnetick direction, it would in some 
MDCCCXXVI. * B b 
