VOL. XIII.] PHILOSOPHICAL TRANSACTIONS. 629 



islands, and all over the Indian Sea from the Cape of Good Hope eastwards, to 

 the middle of the great South Sea that divides Asia from America. This seems 

 to be the present disposition of the magnetical virtue throughout the whole 

 globe of the earth. It remains to show how this hypothesis makes out all the 

 variations that have been observed of late, and how it answers to our several 

 remarks drawn from the table. And first it is plain that (our European north 

 pole being in the meridian of the land's end of England) all places more easterly 

 than that will have it on the west side of their meridian, and consequently the 

 needle, respecting it with its northern point, will have a westerly variation, 

 which will still be greater as we go to the eastward, till we come to some meri- 

 dian of Russia, where it will be greatest, and from thence decrease again* 

 Thus at Brest the variation is but 14°, at London 44-°, but at Dantzic 7° west. 

 To the westward of the meridian of the land's end, the needle ought to have 

 an easterly variation, were it not that (by approaching the American northern 

 pole, which lies on the west side of the meridian, and seems to be of greater 

 force than this other) the needle is drawn thereby westward, so as to counter- 

 balance the direction given by the European pole, and to make a small west va- 

 riation in the meridian of the land's end itself. Yet I suppose that about the 

 meridian of the isle Tercera, our nearest pole may so far prevail as to give the 

 needle a little turn to the east, though but for a very small space; the counter- 

 balance of those two poles permitting no considerable variation in all the eastern 

 parts of the Atlantic Ocean, nor upon the west coasts of England and Ireland, 

 France, Spain, and Barbary. But to the westward of the Azores, the power 

 of the American pole overcoming that of the European, the needle has chiefly 

 respect thereto, and turns still more and more towards it as we approach it. 

 Whence it comes to pass, that on the coast of Virginia, New England, New- 

 foundland, and in Hudson's Straits, the variation is westward : that it decreases 

 as we go from thence towards Europe, and that it is less in Virginia and New 

 England than in Newfoundland and Hudson's Straits. This westerly variation 

 again decreases as we pass over the North America, and about the meridian of 

 the middle of California the needle again points due north; and from thence 

 westward to Yedzo and Japan I make no doubt but the variation is easterly, and 

 half sea over not less than 15°, if there be any truth in this hypothesis of mine. 

 Therefore I propose this as a trial, that the whole may be scanned thereby^ and 

 I conceive it will not be hard to know of the Spaniards how it is, who so fre- 

 quently sail through that ocean, in their return from the Manilla isles. This 

 east variation extends over Japan, Yedzo, East Tartary, and part of China, 

 till it meet with the westerly, which is governed by the European north pole, 

 and which I said was greatest somewhere in Russia. 



