122 Analysis of Scientific Books. 
Il. The Philosophical Transactions of the Royal Society of 
London, for the year 1823, Parr. Il. - 
1, On a New Phenomenon of Electro-Magnetism. By Sir Hum- 
phry Davy, Bart. Pres. R.S. 
This is a contribution of a curious fact to the new and interesting 
science of electro-magnetism, and it is by such contributions 
alone that this infant science can, at present, be expected to make 
any progress to maturity. Sir H. Davy found, that when two wires 
were placed in a basin of mercury, perpendicular to the surface, 
and in the voltaic circuit of a buttery with large plates, and the 
pole of a powerful magnet held either above or below the wires, 
the mercury immediately began to revolve round the wire as an 
axis, according to the circumstances of electro-magnetic rotation, 
discovered by Mr. Faraday. Masses of mercury, of several inches 
in diameter, were set in motion, and made to revolve in this man- 
ner whenever the pole of the magnet was held near the perpendi- 
cular of the wire; but when the pole was held above the mercury, 
between the two wires, the circular motion ceased, and currents 
took place in the mercury in opposite directions, one to the right 
and the other to the left of the magnet. Other circumstances led 
to the belief that the passage of the electricity produced motions 
independent of the action of the magnet, and that the appearances 
“were owing to a composition of forces. 
The form of the last experiment was inverted, by passing two 
copper wires through two holes, three inches apart, in the bottom 
of a glass basin; the basin was then filled with mercury, which 
stood about the tenth of an inch above the wire. Upon making a 
communication through this arrangement, with a powerful voltaic 
circuit, the mercury was immediately seen in violent agitation; 
its surface became elevated into a small cone above each of the 
wires; waves flowed off in all directions from these cones, and 
the only point of rest was apparently where they met in the centre 
of the mercury, between the two wires. On holding the pole of a 
powerful magnet at a considerable distance above one of the cones, 
its apex was diminished and its base extended. Ata smaller dis- 
tance, the surface of the mercury became plane, and rotation 
slowly began round the wire. As the magnet approached, the 
rotation became more rapid; and when it was about half an inch 
above the mercury, a great depression of it was observed above the 
wire, and a vortex which reached almost to the surface of the wire. 
The President thinks that these phenomena are not produced by 
any changes of temperature, or by common electrical repulsion, 
and concludes that they are of 2 novel kind. 
