THE GYROSCOPE. 277 



or inverted current produced by the stopping of the machine, the inventor 

 has contrived a circuit breaker on the principle of the electro-magnet, the 

 magnets holding the circuit breaker in contact so long as the machine is 

 working ; but the decrease of velocity lessening the attractive power of the 

 magnet, the circuit breaker opens by its own weight (or a counter-weight) 

 and all danger of a reverse current is obviated. Experimental machines are 

 manufactured by Brequet & Cie (Paris), composed of Jamin's magnets, and 

 turned with a handle, and produce a force of eight Bunsen cells. 



A great revolution, or rather the beginning of a new era in the history of 

 electricity, may be said to have commenced with the perfection of M. Faure's 

 accumulators. These are troughs containing eleven lead plates, each coated 

 with oxide of lead and wrapped in felt, the fluid being dilute sulphuric acid. 

 The application of them to the electric light is one of their most valuable 

 features ; at the depot in. the Strand, where they may be seen at work, there are 

 thirty such elements, each weighing about 50 Ibs. It takes a two-horse-power 

 engine working an Edison or Gramme machine six to eight hours to charge 

 them, and when charged they will keep almost any number of lamps of 

 sixteen-candle-power going some eight hours. They are used on the 

 Brighton and South Coast Railway, and seem peculiarly adapted to lighting 

 by incandescence, by Swan, or Edison's lamp. The elements fully charged 

 may be carried any distance without losing their electric power. And the 

 stored force may be used for charging the accumulators themselves afresh 

 from the machine. These accumulators may be seen any day at 446, Strand, 

 and are well worth a visit. 



The Gyroscope, though now an instrument common and familiar to all 

 students, is none the less the subject of a problem, the solution of which 

 is still to seek. It has indeed been entitled the paradox of mechanics ; for 

 though it depends on gravitation, gravitation yet appears indifferent to it. 

 In order to render the operation of the Gyroscope as continuous as possible, 

 so as to facilitate the profound study of its working, and also to unite 

 another influence with those of the ordinary Gyroscope, producing pheno- 

 mena of which this instrument affords us the spectacle, a learned American 

 has employed electricity as a motive power. 



The Gyroscope, shown in fig. 277, has a large, heavy pedestal, with a 

 pointed column, which supports the instrument itself. The frame, of which the 

 electro-magnets form a part, is connected with a rod, having at one end a hollow 

 cavity which rests on the point of the vertical column. One of the extremities 

 of the magnetic spool is attached to this cavity, the other end communicating 

 with the bar which unites the two magnets. Over this bar is a spring which 

 breaks the current, supported by an insulator in hard india-rubber; itisadjusted 

 so that it touches a small cylinder on the axis of the wheel twice during every 

 rotation of the latter. The wheel's plane of rotation is at right angles with the 

 magnets, and it carries an armature of soft iron, which rotates close to the 

 magnet without touching it. The armature is so placed in relation to the 

 surface of contact with the cylinder that breaks the current, that twice 



