58 GENEKA.L PROPERTIES OF LIVING TISSUES 



arrange themselves in concentric circles around 

 the wire, particularly if the card be gently 

 tapped. 



The position of these "lines of force" shows 

 the direction of the magnetic force, and their 

 number is an index of its intensity. 



To produce Electric Induction, the Lines of 

 Magnetic Force must be cut by the Circuit. 

 Hold the magnet at right angles to the axis of 

 Ae coil, and, keeping it in this position, rapidly 

 advance it towards the coil. 



The electrometer will show no current, because 

 the number of the lines of magnetic force which 

 pass through the field of the conductor has not 

 been altered. 



Electro-magnetic Induction. An electro-magnet 

 may be used in place of the bar magnet to pro- 

 duce induction. 



Connect a dry cell through a simple key with 

 posts 1 and 2 of the primary coil. 1 Close the 

 key. 



When the current passes through the primary 

 coil, the core of iron wire in the coil will be 



1 It will be convenient to use the numbers 1 and 2 to desig- 

 nate th6 posts connected directly with the ends of the primary 

 wire, excluding the vibrating hammer ; the numbers 2 and 3 

 will indicate the posts that connect with the ends of the pri- 

 mary wire including the hammer. When the battery is con- 

 nected with posts 2 and 3 the hammer will vibrate. 



