416 Miscellaueotis Intelligence. 



that the two cylinders form, as it were, a circular cell for acid : 

 a piece of metal is fastened from side to side, like a bridge, 

 across the top of the smaller cylinder, and from the middle of 

 it rises a piece of wire, supporting at its top a small metal cup, 

 containing mercury. A short cylinder of zinc is then procured, 

 of a size that will permit it to go freely into the copper cell 

 before described : a wire, in the form like the letter U inverted 

 ([l), is soldered to it at opposite sides, and in the bond of this 

 wire a metallic point is fixed, which, when placed in the little 

 cup of mercury before described, suspends the zinc cylinder freely 

 in the copper cell; then weak acid being put into the cell, the zinc 

 and copper form a voltaic combination, and the two sides of 

 the fi wire are both in the same state, so that the pole of a small 

 magnet placed in the cylinder, that is left open in the axis of 

 the apparatus, makes the wire, and the zinc cylinder with it, 

 revolve. If the apparatus be 9 or iO inches in diameter, it is 

 stated that there is a tendency to rotation by the action of the 

 terrestrial magnetism alone. 



5. Note on New Electrc-Magneiical Motions, by M. Faraday, 

 — At page 96 of this volume, I mentioned the expectation I 

 entertained of making a wire through which a current of voltaic 

 electricity was passing, obey the magnetic poles of the earth in 

 the way it does the poles of a bar magnet. In the latter case it 

 rotates, in the former I expected it would vary in weight ; but 

 the attempts I then made, to prove the existence of this action, 

 failed. Since then I have been more successful, and the object 

 of the present note is so far to complete that paper, as to shew 

 in what manner the rotative force of the wire round the ter- 

 restrial magnetic pole, is exerted, and what the effects produced 

 by it, are. 



Considering the magnetic pole as a mere centre of action, the 

 existence and position of which may be determined by well- 

 known means, it was shewn by many experiments, in the 

 paper, page 74, that the electro-magnetic wire would rotate 

 round the pole, without any reference to the position of the 

 axis joining it with the opposite pole in the same bar; for some- 

 times the axis was horizontal, at other times vertical, whilst the 

 rotation continued the same. It was also shewn that the wire, 

 when influenced by the pole, moved laterally, its parts de- 

 scribing circles in planes perpendicular nearly to the wire 

 itself. Hence the wire, when strait and confined to one point 

 above, described a cone in its revolution, but when bent into a 

 crank, it described a cylinder ; and the effect was evidently in 

 all cases for each point of the wire to describe a circle round 

 the pole, in a plane perpendicular to the current of electri- 

 city through the wire. In dispensing with the magnet, used 

 to give these motions, and operating with the terrestrial mag- 



