340 Proceedings of the British Association. 



lieve that more cannot be expected from a mechanical force, 

 whose existence has only been known since 1834, when I made 

 the first experiment at Konigsberg, in Prussia, and only succeed- 

 ed in lifting a weight of about 20 ounces, by even this electro- 

 magnetic power. 



" I must on the present occasion, confess frankly that hitherto 

 the construction of electro-magnetic machines has been regulated 

 in a great measure by mere trials ; that even these machines con- 

 structed according to the indisputable laws established with re- 

 gard to the statical effects of electro-magnets, have been found in- 

 efficient, as soon as we came to deal with motion. Being always 

 accustomed to proceed in a legitimate manner, and feeling great 

 regret at the irregular attempts which were being made every 

 where, without any scientific foundation, this state of things ap- 

 peared to me so unsatisfactory, that I could not but direct all my 

 efforts to ascertain clearly the laws of these remarkable machines. 

 I submit the formulae relative to these laws, which appear to me 

 to recommend themselves as much by their simplicity as by the 

 natural manner in which they develope themselves. Let R rep- 

 resent all the mechanical resistances acting upon the machine, 

 and V the uniform velocity with which it moves ; we have for 

 the power or mechanical effect, the expression T = Ry. Let w 

 be the number of coils of the helix which covers the rods ; z the 

 number of the plates of the battery ; B the total resistance of 

 the galvanic circuit ; E the electro-motive force : k a coefficient 

 which depends on the arrangement of the bars, the distance of 

 the poles, and the quality of the iron ; we have then for the max- 

 imum of the mechanical effect which will be obtained, the ex- 

 pression, 



^- ^'"~ 4B^' 



For the velocity, which corresponds to this maximum, 



B 

 kn- 

 For the resistance acting upon the machine, 



n-z-^~ 



III. R=-4gr- 



Lastly for the economic effect, i. e. the duty or the mechanical 

 effect divided by the consumption of zinc in a given time, 



IV. 0=1- 



