470 Mr. Raine}''s Reply to Dr. Ritchie's Remarks 



guous one by the permanent magnet, and not from the per- 

 manent magnet itself. 



As the magnetism, then, at one extremity of B may be 

 considered as immediately resulting from the induction on the 

 other, it is highly probable that the inducing power of both 

 is equal. This appears evident from the following experi- 

 ment. Apply a piece of soft iron to either pole of magnet 

 and ascertain the weight it will sustain; then apply another 

 piece to the remote end of the former one, and it will be found 

 to sustain nearly the same weight. This experiment will be 

 influenced somewhat by the form and size of the pieces of iron, 

 by the state of the surfaces in contact, and by any condition 

 of the metal which could interfere with the free and equable 

 distribution of magnetism throughout its substance. It is 

 only when every obstacle to free induction vanishes that the 

 magnetism of the keeper B will be correctly represented by 

 a + b. Now, admitting that under these circumstances {a + b) 

 is a correct expression for the magnetism of the keeper, when 

 it is in contact with the S pole, the same expression would be 

 correct if it were applied to the N pole; and as there is no 

 known limit at which soft iron ceases to allow of further in- 

 duction by an increase of the inducing power, we niust admit 

 that the magnetism of the armature when under the inducing 

 influence of both poles, will be double that which it had when 

 exposed to the action of one pole only, and consetjuently re- 

 presented by 2 (« + b). This will account for the fact of the 

 attraction of the keeper when in contact with both poles of a 

 horse-shoe magnet, at the same time so very far exceeding 

 that which it has for the two poles when applied separately. 



Dr. Ritchie asserts that it is impossible for the lifter by its 

 reaction to increase the power of an electro-magnet, because 

 the lifter, having ol)tained all its magnetism from the electro- 

 magnet, cannot give back more than it has received. Now, 

 the following experiment will prove beyond all doubt that the 

 lifter can increase the power of the electro-magnet; con- 

 sequently by the converse of Dr. Ritchie's reasoning it may 

 be inferrecl that the keeper can be made to possess a 

 higher magnetic state than the electro-magnet to which it 

 applied, which is perfectly consistent with the above reasoning. 

 Heat a common horse-shoe magnet to whiteness, for the pur- 

 pose of totally destroying its magnetism and rendering it more 

 easy of induction. Pass a piece of insulated copper wire 

 around it, in the manner of an ordinary electro-magnet, and 

 let this magnet be exposed to the action of a galvanic battery, 

 when it will be found to have acquired a small (juanlity of 

 magnetism. Keep up the galvanic action until the magnet 



