204 Mr. W. Sturgeon on the Theory of Ma gnetic Electricity. 



direction with regard to the polar magnetic lines, the more 

 rapid the motion the greater will be the degree of excitation, 

 or electro-momentum produced ; and vice versd, the slower the 

 motion the less will be the degree of excitation. Consequently, 

 when the velocity is at a minimum or nothing, no excitation 

 whatever can exist. 



Illustration. — If the excited body be of such dimensions as 

 to have the whole of its natural electric fluid put into motion 

 by the process, the electro-momentum Would always be pro- 

 portional to the velocity, because of the quantity of fluid in 

 motion being constantly the same: and as by Position 2. the 

 motion of the fluid depends upon the motion of the excited 

 metal, the velocity of the former will at all times depend upon 

 that of the latter ; and consequently the electro-momentum or 

 extent of excitation will be proportional to the velocity of the 

 moving body under excitation. 



There may possibly, however, be a limit to the extent of 

 excitation by an increase of motion, when the velocity is very 

 great, in consequence of the yielding of the exciting magnetic 

 lines to the force of the moving body, or to its electric fluid 

 whilst striking them with great rapidity. But as far as my 

 experiments and observations have been conducted, I am led 

 to believe that the electro-momentum may be exalted -by an 

 increase of motion until the velocity becomes exceedingly 

 £rreat; avdiaf * w 4oq gnrtbxs siij lo ai: 



Position 4. — When the velocity of the moving body, and 

 the energy of the exciting polar magnetic lines are constant, 

 the maximum of excitation will be accomplished by the body 

 moving at right angles to those lines against which it im- 

 pinges. 



Position 5. — When the direction in which the body moves 

 is inclined to the axis of the exciting polar magnetic lines at 

 any other angle than 90°, it receives no more excitation than 

 what is due from the quantity of its motion taken in the direc- 

 tion perpendicular to that axis. 



Illustration.-* As the excitation of the body, or of the electric 

 fluid which it contains, depends upon its collision with the 

 polar magnetic lines-, the greater the number of those lines 

 against which the body strikes in a given time, the greater 

 will be the number of exciting impressions accomplished in 

 that time. f " w ' 



Let a b, and a c, (fig. 6.) be two directions in which a piece 

 of metal is caused to move; the former; perpendicular, and the 

 latter oblique to the axis of the group of polar magnetic lines, 

 represented by the vertical lines dashed across their heads 

 in the figure. If now ab as ac represent the velocity in each 



