1 826.] an improved Electro-magnetic Apparatus, 359 



and interesting science ; for whenever an experiment was 

 not attended with the anticipated success, the failure was gene- 

 rally attributed to an insufficiency of galvanic power ; and in 

 order to increase the effect, it appears that the experimenter 

 had no other means of accomplishing his object, than by aug- 

 menting the power of his battery, or by reducing the size and 

 increasing the delicacy of his other apparatus, the magnetic 

 power being either entirely lost sight of, or regardlessly neg- 

 lected, as if no ways materially concerned in the process. 



I have found, however, by the above-mentioned course of 

 experiments, that the magnetic force is as essential as that of 

 galvanism to the development of electro-magnetic phenomena; 

 and the apparatus which I now submit to the attention and 

 impartial consideration of your valuable Society, acting on the 

 principle of powerful magnetism and feeble galvanism, will, I 

 trust, be found more eligible and efficient than any other that 

 has yet been brought before the public. 



Reference to the Engraving of Mr, W, Sturgeon^ Electro-mag- 

 netic Apparatus, (Plate XLI.) 



Plate XLI. fig. 1. A perspective view of an apparatus to show 

 the revolution of a magnet round its own axis, a a the two 

 galvanic apparatuses on their stands b h, they are acting on the 

 magnet N s, by means of the connecting wires dddd; both 

 their copper poles c e are applied to the equator e of the magnet, 

 while the zinc pole z of one is applied to the north pole N, and 

 the zinc pole z of the other is applied to the south pole s of the 

 magnet. A wirey is soldered on to the magnet, and bent down 

 at one end to dip into the circular trough e to form the equato- 

 rial connexion : and as all the connexions are made by mercury 

 and amalgamated wires, the end of this wire is amalgamated, 

 and mercury put into the trough : all the little cups z and c are 

 also amalgamated at the bottom, and contain mercury ; the 

 bottom wires of the zinc and copper poles are likewise amalga- 

 mated to dip in connecting cups when wanted. The magnet 

 has brass wire centers on which it turns, that at the north pole 

 stands in a cup z with mercury ; and the other at the south pole 

 enters the amalgamated hollow in the screwed end of the upper 

 connecting cup z. When the connections are made, as above 

 described, on pouring dilute nitric acid into the troughs a a, 

 the magnet will revolve in the way shown by the arrow ; but on 

 changing the connexions, by applying the copper wires to the 

 poles, and the zinc ones to the equator, it will revolve the con- 

 trary w^ay ; here the magnet only forms the connexion between 

 the electric poles, and revolves around, or with the current 

 which is conducted by it. g gg is the stand which supports the 



