186 Miscellaneous Intelligence. 



an electrical rhachine, and sparks passed to it. After a num- 

 ber of these had been taken, the needle, on examination, 

 proved to be magnetic. — Bib. Univer. xvii. p. 23. 



20. New Electro-Magnetic Apparatus. — Since the pappr in the 

 preceding pages has been printed, I have had an apparatus 

 made by Mr. Newman, of Lisle-street, for the revolutions of the 

 wire round the pole, and a pole round the wire. When Hare's 

 calorimeter was used to connect with it, the wire revolved so 

 rapidly round the pole, that the eye could scarcely follow the 

 motion, and a single galvanic trough, containing ten pair of 

 plates, on Dr. Wollaston's construction, had power enough to 

 move the wire and the pole with considerable rapidity. It con- 

 sists of a stand, about three inches by six, from one end of 

 which a brass pillar rises about six inches high, and is then 

 continued horizontally by a copper rod over the stand ; at the 

 other end of the stand a copper-plate is fixed with a wire for 

 communication, brought out to one side ; in the middle is a 

 similar plate and wire ; these are both fixed. A small shallov/ 

 glass cup, supported on a hollow foot of glass, has a plate of 

 metal cemented to the bottom, so as to close the aperture, and 

 form a connexion with the plate on the stand ; the hollow foot 

 is a socket, into which a small cylindrical bar magnet can be 

 placed, so that the upper pole shall be a little above the edge of 

 the glass ; mercury is then poured in until the glass is nearly 

 full; a rod of metal descends from the horizontal arm perpen- 

 dicularly over this cup ; a little cavity is hollowed at the end 

 and amalgamated, and a piece of stiff copper wire is also 

 amalgamated, and placed in it as described in the paper, except 

 that it is attached by a piece of thread in the manner of a liga- 

 ment, passing from the end of the wire to the inner surface of the 

 cup ; the lower end of the wire is amalgamated, and furnished 

 with a small roller, which dips so as to be under the surface of 

 the mercury in the cup beneath it. 



The other plate on the stand has also its cup, which is nearly 

 cylindrical, a metal pin passes through the bottom of it, to 

 connect by contact with the plate below, and to the inner end 

 of the pin a small round bar magnet is attached at one pole by 

 thread, so as to allow the other to be above the surface of the 

 mercury when the cup is filled, and have freedom of motion 

 there ; a thick wire passes from the rod above down perpendi- 

 cularly, so as to dip a little way into the mercury of the cup ; 

 it forms the connecting wire, and the pole can move in any di- 

 rection round it. When the connexions are made with the 

 pillar, and either of the wires from the stand plates, the revo- 

 lution of the wire, or pole above, takes place ; or if the wires 

 be connected with the two coming from the plates, motion takes 

 place in both cups at once, and in accordance with the law 



