443 Mr. H. Wilde on some Improvements in 



the erroneousness of this view, and also that my discovery bears 

 only the same kind of relation to that of Faraday as that philo- 

 sopher's discovery does to those of Galvani, Volta, and Grove in 

 galvanic electricity, and of CErsted, Ampere, Arago, and Stur- 

 geon in electromagnetism. That the discovery of the indefinite 

 increase of the magnetic and electric forces from quantities in- 

 definitely small is a fundamental advance in electrical knowledge, 

 and not simply an expansion of known principles, or an improve- 

 ment in a machine (as it has been made to appear by some), is 

 evident from the fact that the principle, since its enunciation in 

 1866, together with my invention of minor and major magneto- 

 electric circuits, has been embodied in the machines of different 

 forms constructed by Ladd, Holmes, D'lvernois, Gramme*, and 



* Comptes Rendus de V Acad, des Sci. July 1871, December 1872. A 

 novel feature in the machine constructed by M. Gramme is an attempt to 

 arrive at a nearer approximation to the continuous current of the voltaic 

 battery than that produced from a magneto-electric machine when rectified 

 by means of a commutator of the ordinary construction. This refinement, 

 however, possesses little or no advantage in any of the applications of mag- 

 neto-electricity when the rectified waves succeed each other at the rate of 

 5000 per minute and upwards — a rate of succession easily attainable, and 

 far exceeded by. the machines of Berlioz and Holmes. At this rate the dis- 

 continuity of the waves is not distinguishable in the electric light, nor in 

 the magnetization of electromagnets, nor on galvanometer needles, nor in 

 electrolytic processes ; and it can only be perceived by the vibrations of a 

 steel spring placed before the poles of a small electromagnet round which 

 the current is transmitted. Such instrument would, I think, also indicate 

 similar points of maxima and minima in the current from Gramme's ma- 

 chine. As the armature-helices in this machiue are each connected with 

 separate pieces of metal, forming the segments of a circle, from which the 

 current is taken by means of ordinary metallic brushes, the number of he- 

 lices producing currents available for external use at any given moment is 

 only a fraction of those constituting the whole circle ; and consequently 

 for a given weight of materials such a magneto-electric machine must 

 be greatly inferior in power to machines in which the current is delivered 

 from the whole of the helices simultaneously, as in those hitherto con- 

 structed. The substitution, by M. Gramme, of a commutator with mul- 

 tiple segments insulated from each other and having adjacent segments of 

 the same polarity, while those diametrically opposite have a polarity differ- 

 ent, requires the same precautions to be taken to prevent the spark at the 

 change of contacts, and is subject to the same wear from friction as com- 

 mutators of the ordinary form, in which the segments are united with a 

 common metallic base. Moreover, long experience has proved that, for the 

 production of electric light, the alternating current is greatly superior to 

 the continuous one — as commutators are dispensed with, and it has the 

 important advantage of consuming the carbons equally, and thereby always 

 retains the luminous point in the focus of any optical apparatus used in 

 connexion with it. 



In short, M. Gramme, in his endeavour to reconcile the incompatible 

 relations of the voltaic current and the magneto-electric wave at the in- 

 stant of its generation, has, by inverting the order and functions of the 

 organic parts of an ordinary magneto-electric machine and suppressing the 

 action of a number of the armature-helices, brought about results retro- 



