232 SCIENTIFIC AND TECHNICAL LABOURS TO 1860. 



currents of both halves were taken up and united into 

 a continuous current. This contact is effected by means 

 of brushes, which are moved round by the prolonged 

 axis of the iron cone. 



The i 'plate" machine was constructed by me in 

 1854 and shown at several Universal Exhibitions, first 

 at the one held in Paris in the year 1855. One of 

 them together with other apparatus of our construc- 

 tion is preserved in the museum of the Berlin Post 

 Office, which probably possesses the most complete 

 collection of old telegraphic apparatus anywhere to be 

 found. The <; plate"' machine is interesting, because it 

 represents the first solution of the problem, how to 

 generate by induction continuous currents in one 

 direction, and follows precisely the same course as 

 that taken by Professor Pacinotti ten years later in 

 constructing his famous magneto-inductor: the principle 

 of current ramification, which is carried out in the 

 ring of Pacinotti, being already contained in it. My 

 machine is thus the precursor of the modern dynamo 

 machine with continuous current and at the same 

 time of the transformer. Had the self-motion of the 

 plate not been made a point of, and had it been 

 effected by mechanical revolution of the axis together 

 with the brushes, an effective dynamo-electric machine 

 would even then have been obtained, and the inter- 

 vening period of the employment of the Siemens" 

 armature would have been skipped. This may serve 

 as an instance of the difficulty which is often ex- 

 perienced in first apprehending the most obvious 



