ELECTKO-MAGXETIC PULSATIONS. 



the right or left. Let t if be two stops, placed a small distance to 

 the right and left of its extremity, g, so as to limit the range of 

 its play. Let s be a spring attached to the extremity, A, by 

 which that extremity will be constantly drawn to the left, and 

 therefore the opposite extremity, g, thrown to the right against 

 the stop, t. When the current is suspended, and the rods, m m', 

 divested of magnetism, the lever yielding to the action of the 

 spring, s, the end, <?, will rest against the stop, t. But when the 

 current passes on the wire, the rods, m m', becoming magnetic, 

 will attract the arm, o g, of the lever, and this attraction 

 exceeding the force of the spring, the arm, og, will be drawn 

 towards the electro-magnet, until it encounters the stop, t', against 

 which it will rest so long as the current continues to flow. But 

 the moment the current is suspended, the bars, m m', suddenly 

 losing their magnetism, the lever, o g, is abandoned to the action 

 of the spring, and it is again thrown back upon the stop, t, where 

 it rests until the current is re-established. 



Let us suppose that an agent at the station, s, to which the 

 wire, a b, extends, and which may be at any distance, 500 miles 

 for example, from s", is supplied with any of the means which 

 have been explained, by which he can at will control the pulsa- 

 tions of the current. When he causes the current to flow, he 

 imparts magnetism to the bars, m m', and throws the lever, o g, 

 against the stop, if . When he suspends the current he deprives 

 the bars, m m', of their magnetism, and leaves the lever, o g, to 

 the action of the spring, s, by which it is thrown against the 

 stop, t. 



It appears, therefore, that with each pulsation which the current 

 receives from the agent at s, the lever, o g, at s", 500 miles distant 

 from him, will perform a vibration between the stops, t and t . 

 As the transmission and suspension of the current, and also the 

 acquisition and loss of the magnetic power, by the rods, m m', are 

 both instantaneous, there is no practical limit to the velocity of 

 the pulsations of the current and those of the magnetism alternately 

 acquired and lost by the rods, m m 1 . The oscillations of the lever, 

 o g, produced by these pulsations are limited, however, by the 

 weight of the lever, the force of the spring, and the distance 

 between the stops, t and f . The greater the weight of the lever, 

 the force of the spring, and the distance between the stops, the 

 slower will be the motion of the lever from t to f, produced by a 

 current of given intensity. The greater the weight of the lever, 

 and the distance between the stops, and the less the force of the 

 spring, the slower will be the motion from t' to t. 



The stop, tf , is so placed as to prevent the absolute contact of 

 the arm of the lever with the electro-magnet, but to allow it to 



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