TO THE MOVEMENT OF MACHINES. 305 



2. 



In May 1834 I constructed the first magnetic apparatus with a pri- 

 mitive continuous circular motion. It is true that, like M. dal Negro, 

 (with whose labours I regret that I am not better acquainted,) I had 

 several years ago conceived the idea of applying this power to mecha- 

 nics : but I could not at first divest myself of the idea of making this 

 application by means of an advancing and receding motion, produced 

 by the attractive and repulsive power of magnetic bars, — amotion which, 

 by known means, might have been changed into a continuous circular 

 one. It seemed to me that an apparatus of this kind would have 

 only the merit of an amusing toy, which might find a place in the cabi- 

 nets of men of science, but would be entirely inapplicable on a large 

 scale with any advantage. 



For considering tlie general equation of active forces applied to the 

 movement of machines 



2 /'^ Mds — ^r\ Pds' = 'Zjnv^— ^mv^ 



the magnetic action, during the amplitude a, and represented by 



/Mds, could not be perfectly exhausted by the action 2 / Pds', 

 O l/ 



unless the active force gained during the movement becomes zero, 



or Hint V, — Smw =0. Now the magnetic attraction is a function of 



the space, the form of which we do not sufficiently know, this function 

 being affected by the nature of the distribution of the magnetism in the 

 body, of whatever form. The law of this distribution is scarcely esta- 

 blished with regard to bars of steel of a regular form, magnetized to 

 saturation and deprived of consecutive points. With regard to bars of 

 soft iron of considerable dimensions, magnetized by an electro-con- 

 ductive helix, we have analogies only, but no experiments. But however 

 this may be, we know well that this function must be expressed by a very 

 convergent series, so that the magnetic attraction will be in an inverse 

 proportion to the square or to the cube of the distance, or, stopping at 

 the three first members, will perhaps be composed of them. The mag- 

 netic points then approach each other with an accelerated motion ; the 

 active forces increase, and reach their maximum at the instant when the 

 contact is completed : but this force ought then to be destroyed. It 

 will destroy itself by the fixed points of the machine, and by the vibra- 

 tion of the system : but this will be in an unprofitable manner. There 



- 2 



will be a complete loss of the active force obtained 2m r, — I,niv . We 



o 

 know the ill effects of shocks in the movement of machines, but there is 

 here aiiotiier inconvenience wliicli is not simply mechanical. The soft 

 iron, by these rcpi'ated shocks and vibrations, gradually acquires at the 



