6 li. VV. Fox on Electrical Action. 



tension, added to the reciprocal lateral repulsion of the ter- 

 minating poles of the magnetic elements, must, I conceive, im- 

 part to the different series of them within a magnet, a curvi- 

 linear arrangement, the convex sides of the curves being turned 

 towards its axis; and the very tenacious manner in which the 

 particles of loadstone so long retain their divergency at a pole 

 of a magnet, when strongly attracted by another magnet, is, 

 I think, only to be explained by a reference to this reciprocal 

 repulsion of the elementary poles, and the tension produced 

 by the external magnetic curves. 



That these magnetic curves extend to an extraordinary di- 

 stance from a magnet, may be easily proved by their sensible 

 action on a very minute and delicately suspended needle, 

 which has been neutralized wifh respect to the directive force 

 of the earth's magnetism. On using this test I found that a 

 magnet, 3 inches long and y^th of an inch in diameter, was 

 invested with a magnetic sphere, (if I may use the expression,) 

 which occupied considerably more than a million times its own 

 bulk, ample allowance having been made for the space filled 

 by the magnetic curves round the suspended needle itself. 



This fact, taken in connexion with the rapid decrease of 

 the force of a magnet at very minute distances, and the inap- 

 preciable change in the earth's magnetic intensity* at the 

 greatest distances above and below its surface which have 

 been examined, go far to show that the influence of the ter- 

 restrial magnetism may probably extend to a vast distance 

 from our globe; and if the magnetic forces be common to 

 the planetary system, the remarkable uniformity in the places 

 of the nodes of most of the planets in relation to the plane of 

 the solar equator may, perhaps, be referred to their agency. 



I am unwilling to conclude this communication without re- 

 marking, that the fact I have stated relative to the particles 

 of loadstone attached to the end of a magnet having their 



* From numerous experiments which I have made at various times, in 

 addition to what others have done, I have no doubt of the fact of there 

 being very small apparent temporary fluctuations in the terrestrial magnetic 

 intensity by day, and occasionally by night ; although these changes may 

 be due merely to variation in the magnetic dip. Among the local affections 

 of the magnetic needle, I will mention one instance which my relative 

 Arthur K. Barclay has communicated to me. In a tour of pleasure which 

 he last year took through Italy, Sicily, Greece, Turkey, &c, he kindly 

 made, at my request, many observations with a horizontal needle de- 

 flected by a magnet in a fixed relative position; and at the base of Trizza t 

 or the Cyclops Rocks, he observed a deflection of 24°, whereas at their 

 summit it was 30°. The former consists of columnar basalt, and the latter 

 of sandstone. My friend repeated these observations several times with 

 the same results. At Messina, Catania, &c, the deflection of the needle 

 was also 30°. 



