Polytechnic Association Proceedings. 593 



The lecturer spoke of the corona observed during the last total 

 eclipse of the sun, which he attributed to its atmosphere, and it 

 was on calculations founded on those appearances that the height 

 of the sun's atmosphere had been conjectured. i 



CONVERSION OF DYNAMICAL INTO ELECTRICAL FORCE. 



W. and C. W. Siemens, of England, have modified the machine 

 invented by Mr. Wilde,, by substituting electro-magnets for the 

 permanent or steel magnets in the primary magneto-electric part 

 of the apparatus. The electro-magnets are first charged by a gal- 

 vanic battery or other rheomotor; after the armature begins to 

 ix>tate, the battery is removed, and without its aid the magnetic 

 force continues to accumulate. It is not essential even to use the 

 battery, for the soft iron in the core of the electro-magnet may bo 

 chai-ged by contact with a permanent magnet, to be removed after 

 the armature is in motion. 



Wheatstoue has also constructed an apparatus in which the wires 

 covering the electro-magnets are connected with those surrounding 

 the armature by which the current, while moving in the same direc- 

 tioa, is made to act upon the electro-magnet so as to increase its 

 polarity; the residual magnetism of the iron — the primary cause 

 of the current — increases until it reaches its maximum. To pro- 

 duce this increase of the intensity of the induced current, there 

 must be a vast augmentation of the force required to turn the 

 armature. 



M. G. Fanner, of Salem, Mass., has made similar and more inter- 

 esting modifications of the original machine, and in a letter to Mr.' 

 Wilde, the inventor, he states that he has obtained an increase of 

 thirty per cent in the power of the magneto-electric machine, by 

 trausmittino^ the current from the armature throuffh the coils of 

 wire surrounding the pieces of soft iron, forming the prolonged 

 extremities of the permanent magnets of the machine. He con- 

 stmcted, also, a small machine, in which a current from a thermo- 

 battery excites the electro-magnet of the Wilde machine to start it. 

 and, after the machine is in action, a branch from the current of 

 the magnets passes through its own electro-magnet, and thus sup- 

 plies the magnetism required. It is not exactly like a person 

 standing in a basket and trying to lift himself, because the electri- 

 city proceeds from a conversion of mechanical energy which must 

 ,be continually supplied. Neither can it be in anywise likened to 

 the various schemes for producing perpetual motion; but it depends 



[Inst.] 38 



