206 Mr. W. Sturgeon on the Theory of Magnetic Electricity. 



poles) will be upwards, and may very conveniently be repre- 

 sented by the group of small crosses embraced by the ring. 

 (Fig. 8. is an oblique view of fig. 7.) j' t 1 



It now the ring be put into motion in its own plane, it will 

 be a matter of no consequence which side advances towards 

 the centre ; the electric current thus excited wi\\flow in every 

 part of the ring in one and the same direction ; which direction 

 is indicated by the four exterior arrows, fig. 7. 



Now, as the group of polar magnetic lines is stationary, and 

 encompassed by the ring, it will be that part only of the ring, 

 which advances towards the centre or axis of the group, which 

 will receive the exciting impressions. The opposite side, in- 

 stead of impinging on the polar magnetic lines, absolutely re- 

 cedes from them, and operates in no other capacity than that 

 of conductor to the excited current in the advancing side. 

 So that whether it be a 9 b 9 c 9 or d which advances towards the 

 centre, their opposite sides c 9 d 9 a 9 or b will respectively recede 

 from the axis of the group, and become conducting parts of 

 the ring, whilst the former correlative parts are receiving the 

 exciting impressions. 



Fig. 9. represents the ring cut open in four places, and each 

 part made perfectly straight to represent four separate pieces 

 of wire. 



Let any one of these wires advance towards the centre of 

 the group of polar magnetic lines. Then as the excitation in 

 this case is under precisely the same circumstances as in the 

 former, the electric current in the advancing wire, or part of 

 the ring, is also constant and uniform in its primitive direc- 

 tion, flowing in one and the same invariable course, relatively 

 to the exciting polar magnetic lines which gave it birth and 

 activity. (See the arrows in fig. 9.) 



To familiarize still further this beautiful law of magnetic 

 electricity : Let any man suppose himself to be placed in the 

 axis of a group of polar magnetic lifies, similarly situated to 

 those in fig. 7. and 8. Let him now stand or suppose him- 

 self to be standing in the centre of a hoop or ring of metal. 



Whilst in this position, let him permit the ring to move 

 in its own plane. Consequently, some part ol it will advance 

 towards him, whilst the opposite part will recede from him. 

 The former will receive the exciting impressions, and the latter 

 will become a portion of the conducting circuit. 



Let him now look to whatever side of the ring he pleases, 

 the current before him will be flowing from his right to his 

 left hand. 



If it be the excitation of a straight wire which he is con- 

 templating, let him consider it as a portion of the original 



