168 Transactions of the American Institute. 



ever, to observe whether future appearances corresponded thereto, 

 and this has been found invariably the case, as related in the observa- 

 tions." 



We now give the previous surmises of Dr. Halley, contained 

 in these extracts, from his very ingenious and suggestive paper, which 

 I found in the transactions of the Royal Society, "An account of the 

 late surprising appearances of the lights seen in the air, on the 6th of 

 March last ; with an attempt to explain their principal phenomena. 

 Anno 1716." 



" But without inquiring how sufficient the Cartesian hypothesis 

 may be for answering the several phenomena of the magnet, that the 

 fact may be better comprehended, we shall endeavor to exhibit the 

 manner of the circulation of the atoms concerned therein, as they are 

 exposed to view, by placing the poles of a terella or spherical magnet 

 on a plane, .as the globe on the horizon of a right sphere ; then, 

 strewing fine steel dust or filings very thin on the plane all round it, 

 the particles of steel, on a continued gentle knocking on the under 

 side of the plane, will by degrees conform themselves to the figures 

 in which the circulation is performed. Thus, * * * by 

 doing as prescribed, it will be found that the filings will lie in a right 

 line perpendicular to the surface of the ball, when in the line of the 

 magnetical axis continued. But, for about forty-five degrees on either 

 side, they form themselves into curves, more and more crooked as 

 they are removed from the poles, and more and more oblique to the 

 surface of the stone. As the figure truly represents, and as may 

 readily be shown by the terella and apparatus for that purpose, in the 

 repository of the Itoyal Society. 



" Now, by many and very evident arguments it appears that our 

 globe of earth is no other than one great magnet. * * 



It suffices, that we may suppose the same sort of circulation of such 

 an exceedingly fine matter to be perpetually performed in the earth, 

 as we observe in the terella, which subtile matter freely pervading 

 the pores of the earth, and entering into it near its southern pole, 

 may pass out again into the other, at the same distance from the 

 northern, and with a like force, its direction being still more and 

 more oblique, as the distance from the poles is greater. , To this we 

 beg leave to suppose, that this subtile matter, no otherwise discover- 

 ing itself but by its effects on the magnetic needle, wholly impercep- 

 tible, and at other times invisible, may now and then, by the con- 

 course of several causes very rarely coincident, and to us as yet 

 unknown, be capable of producing a small degree of light ; perhaps 



