Mr. W. Sturgeon on the Theory of Magnetic Electricity. 205 



direction, then those two lines will also represent the spaces 

 through which the body moves in two equal portions of time. 

 Now it is evident, by mere inspection of the figure, that whilst 

 the body moves from a to b, in the direction perpendicular to 

 the axis or general direction of the polar magnetic lines, it 

 will have to impinge against a greater number of those ex- 

 citing lines than whilst moving in the oblique direction from 

 a to c. Or, the body will impinge on no greater a number of 

 polar magnetic lines whilst passing obliquely from a to c, with 

 the velocity ac, than it would strike by moving with the less 

 velocity a d —fe, the quantity of its motion taken in the per- 

 pendicular direction a b. noqu zbmtp 



But, as the velocity is supposed to be constant in both di- 

 rections, then the same number of exciting impressions will 

 be accomplished by the body being in motion during a part, 

 a d, only of the time, ab, in the perpendicular direction ab, as 

 will be accomplished by its being kept in motion the whole of 

 the time ac = ab, in the oblique direction ac. 



Corollary. — Hence it is evident, that if a metallic body were 

 to move in the direction of the axis of a group of parallel 

 polar magnetic lines, it would suffer no excitation whatever. 

 The position is also conformable to experiment. 



Position 6. — The natural or primitive channel of an elec- 

 tric current generated by magnetic agency is at right angles 

 to the axis of the exciting polar magnetic lines, whatever may 

 be the direction in which the excited body moves. -, :< f\ 



Remarks. — The current may, however, be led or con- 

 ducted in various other directions, according to the figure and 

 dimensions of the metal employed, and the various directions 

 in which it may be put into motion ; notwithstandiug which, 

 the primitive channel of the current will be constantly the 

 same, — at right angles to the axis of the exciting polar mag- 

 netic lines. 9h>na i^dto vna 



Position 7. — The direction in which the current Jlows with 

 regard to the exciting polar magnetic lines, is constantly the 

 same, whatever may be the direction in which the metal is 

 put into motion, or to whatever extremity or other part of 

 a magnet the metal may be applied M ]j -£^r'*Y ^sVftv^nsrc takut 



Illustration. — Let a, b, c, d (fig. 7.) be a ring of metallic 

 wire, placed with its plane horizontal, and embracing a bundle 

 or group of polar magnetic lines, the axis of which passes 

 through the centre of, and at right angles to, the plane of the 

 ring..jg f£f oq ismiot sdJ javpm oi bo^iics 



Let those magnetic lines emanate from the south magnetic 

 pole of a bar of steel placed beneath the paper on which the 

 figure is drawn. Consequently, their south poles (marked 



