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XXVI. On the Dynamo-electric Current, and on Certain Means to Improve 
its Steadiness. 
By C. William Siemens, D.C.L., F.B.S. 
Received March 1,—Read March 4, 1880. 
[Plates 40-52.] 
On the 14th February, 1867, I communicated a short paper to the Royal Society, 
describing the accumulative or dynamo-electrical principle of action, the conception of 
which I attributed to my brother Dr. Werner Siemens. When the paper was read, 
another paper followed by Sir Charles Wheatstone (sent in on the 24th February) 
also describing this principle of action, thus showing that the same line of thought 
had occupied that eminent philosopher. 
In illustration of my paper I exhibited a machine of my design, embodying the accu¬ 
mulative principle of action, which furnished abundant evidence of the powerful nature 
of the current that could be thus produced. It consisted of two horseshoe electro¬ 
magnets, between the poles of which a Siemens armature could be made to rotate, the 
machine being furnished with a handle or pulley for that purpose. A commutator was 
provided, by which the alternating currents set up in the rotating coil (after a first 
impulse had been given) were directed through the coils of the stationary electro¬ 
magnets in a continuous manner, and proceeded thence outward to ignite a platinum 
wire of some 12 ,/ in length, or to perform other work. 
This machine, although the first of its kind, has done good service ever since its 
construction, having been found very efficacious in exciting powerful permanent 
magnets at the telegraph works of Siemens Brothers at Woolwich. 
Since 1867 the accumulative principle has been employed in the machines of different 
makers, and one form of dynamo-electric machine, that of M. Gramme, differs very 
materially from the machine above referred to, and has met very deservedly with 
extensive recognition. M. Gramme embodied in his machine the principle of Professor 
Pacinotti’s magnetic ring, which enabled him to produce powerful electric currents 
without much of the loss of energy caused in previous machines through the heating 
of the rotating armature. 
Another modification of the dynamo-electrical machine is one devised by Mr. Von 
Heftner Alteneck, an engineer and physicist employed under my brother Werner 
Siemens, at Berlin. This machine differs from that first submitted by myself in 
several important particulars. Instead of the Werner Siemens armature, Von 
Heftner Alteneck adopted a rotating coil of iron wire wound with insulated copper 
wire in more than one direction, the several coils of wire being connected seriatim 
