470 



III order to realise I his in tlie first model slits have been made 

 in llie permanent magnet, which was to procnre the magnetic force. 

 This magnet was snspended between horizontal pivots, in such u 

 way that the lines of force were always kept horizontal. Bj- inserting 

 the axis of rotation through the slits, this axis can be made to be 

 parallel to the lines of force when the direction of the flight is 

 horizontal, while when the machine climbs oi- falls the angle between 

 the lines of force and the axis corresponds to <t in fig. 1. 



The later models had two magnets instead of one, jilaced parallel 

 to each other on both sides of the axis. In both cases the horizontal 

 axis of suspension of the magnet was made to coincide with the 

 line around which the armature axis pivoted. 



If the axis AA (fig. 2) be parallel to the lines of force, no 

 ditference of potential will arise between the ends of the rotating 



A 



'III 2 



winding W. The electromotive force in an element f of the coil is 

 exacti)' counteracted by an equivalent E. M. F. in the opposite 

 sense, generated in the element s' lying in the position of a 

 reflected image with respect to the axis. 



If the axis AA (tig. 3) makes an angle a with the lines of force, 

 an electromotive force will be generated in W proportional not only 



M 



Hg3 



to the speed of rotation and the strength of the field, but caeteris 

 paribus also to sin i<. The magnetic field can be considered as being 



