282 SEC. 9. MAGNETISM. 



1122. Objects illustrating the applications of tubular 

 Electro-Magnets. John Faulkner. 



1. A. Electro-magnets; various. 



2. B. Electric bells ; various. 



3. C. indicators ; various, 



4. D. ,, semaphore actuators ; various. 



5. E. ,, telegraph sounders ; various. 



6. , key and sounder on one base. 



7. 



9. 

 10. 



separate. 



sounder with movable cover. 



with movable core. 



with movable coil. 



11. F. brass and iron separators. 



12. G. pottery glaze iron extractors. 



In the sounders a movable cover of wire is made partially or totally to 

 cover the coil by means of a regulating screw. In case of partial failure of 

 the battery, the instrument can be increased in power by a suitable alteration 

 of the position of the wire cover. 



1123. Froment's Engine. An electro-magnetic machine 

 depending upon the successive .attraction by fixed electro-magnets 

 of bars of soft iron fastened on a wheel and parallel to its axis. 



Frederick Guthrie. 



The successive magnetisation and demagnetisation of the magnets is 

 effected by the action of cams on the axis of the wheel, which lift ivory 

 rollers, and so displace springs to which they are fastened. 



1124. Helmholtz's Electro-magnetic Engine. 



F. Rob. Voss, Berlin. 



The advantage of this machine is that it is set in motion by a very small 

 galvanic force ; with two Bunsen elements it will drive one of Professor 

 Helmholtz's double-syrens or one of his centrifugal commutators. 



Professor Helmholtz has applied a contact-arrangement to the commutator 

 of the Siemens' bobbin, which surpasses all former ones in that it avoids great 

 surfaces of friction, thus attaining greater power and speed. 



1124a. Electro-magnetic Machine, with velocity regu- 

 lator. Helmholtz. 



Physical Institution of Berlin, Prof. Helmholtz. 



The current which drives the electro-magnetic machine is interrupted 

 by the centrifugal regulator whenever the velocity exceeds a certain limit, 

 whereupon the driving force ceases. Using a current which is only a little 

 stronger than what exactly suffices for the normal velocity, exceedingly 

 constant velocities of rotation are obtained. (Described by M. Exner in the 

 Sitzungsberichte of the Vienna Academy, Math. Natura. section, vol. LVIIL, 

 part II., page 602.) 



1125. Electro-magnetic Engine. F. Sto/trer, Leipzig. 



1125a. Electric Motive Power, acting on a pump. 



M. Loiseauj junior , Paris. 



1125b. Electric Motive Power, acting on a jet of water. 



M. Loiseau, junior , Paris. 



