640 PHILOSOPHICAL TRANSACTIONS. [aNNO 1701. 



times, but successively varies that declination from time to time. Which, 

 though it were about that time a new discovery, is now admitted as an un- 

 doubted truth. 



And what is called the dipping needle, is admitted also to be an English dis- 

 covery, somewhat prior to the former ; I cannot say at present whether by Mr. 

 Blagrave, or some other Greshamite. That is, that the magnetic needle, 

 besides its direction toward the north, in its horizontal position, has also a direc- 

 tion of altitude above the horizon ; and, if duly poised about a horizontal axis, 

 will point to a determinate degree of altitude or elevation above the horizon, in 

 this or that place respectively. Of which discovery, though made so long ago, 

 I do not find that much use has hitherto been made, that of its horizontal 

 declination being more serviceable. 



It is also an English observation, that not only a magnetic needle, but any 

 piece of iron, if kept long in the same position, will of itself contract a pola- 

 rity. As for instance, an erect bar in a window, after long continuance in that 

 position will, if duly poised, be found with its upper end to point toward the 

 north, and southward with the other end; and if afterwards it be continued long 

 in a contrary position, it will attain a contrary polarity. 



And Mr. Gilbert's notion, of the earth's whole body being but one great 

 magnet, and lesser magnets being so many terrellas sympathizing with the 

 whole, is English also. — It has been observed also, that a magnetic needle, if 

 heated red-hot, will lose its polarity ; and if then cooled in a contrary position 

 will acquire a contrary polarity. — It has also been observed by our English mari- 

 ners, that upon a great flash of lightning at sea, their magnetic needle has lost 

 its former polarity, and contracted the contrary, pointing the wrong way, and 

 directing the mariner to a wrong course. 



And in general, the doctrine of magnetism has been more improved by our 

 English naturalists than by any other nation. And if some of the Gresham 

 gentlemen would take the pains to give us a true history of these and the like 

 improvements, it would be an acceptable service for the honour of the nation, 

 and of that college in particular, as well as of the Royal Society. 



Account of a Book, viz. — Aloysi Ferdinandi Comit. MarsigU Danubialis Operis 

 Prodromus, Ad Regiain Societatem Anglicanam. Fol. 170O. N° 276, p. 1038. 



Of this book an account has been given, in the life of Marsigli, inserted at 

 pp. 307, 308, of this vol. 



END OP VOLUME TWENTY-SECOND OF THE ORIGINAL. 



