186 
Scientific Intelligence. 
either above or below the wires, the mercury immediately began 
to revolve round the wire as an axis, and with a highly increased 
velocity when the opposite poles of two magnets were used, one 
being above, and the other below. Masses of mercury, several 
inches in diameter, were set in motion, and made to revolve in 
this manner, whenever the pole of the magnet was held near 
the perpendicular 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. Sir 
Humphry next inverted the form of the experiment. He took 
two copper-wires of about Jth of an inch in diameter, the ends of 
which were flat, and carefully polished, and passed them through 
two holes 3 inches apart in the bottom of a glass basin, and per- 
pendicular to it. They were cemented into the basin, and made 
non-conductors by sealing-wax, except at the polished ends. 
The basin was then filled with mercury to the height of ^^th of 
an inch above the wires. The moment the contacts were made, 
the mercury was immediately seen in violent agitation ; its sur- 
face became elevated into a small cone above each of the wires ; 
— waves flowed 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 a powerful mag- 
net some inches above one of the cones, its apex was diminished 
and its base extended : by lowering the pole farther these effects 
were increased, and the undulations became feebler ; and at a 
smaller distance, the surface of the mercury became plain, and 
rotation slowly commenced round the wire. The elevations 
and depressions in some experiments were }th or Jth of an inch. 
— See Phil. Trans. 1823, p. 156. 
METEOllOLOGY. 
13. Mean Temperature of London for 1822. — It appears 
from the Meteorological Journal kept in the Royal Society’s 
apartments, and just published, that the mean temperature of 
London by Six’s thermometer is 55 ^ Fahrenheit, and by obser- 
vations made at 8 a. m. and 2 r. m. that it is 53^.8, results 
which appear to be perfectly irreconcilable Avith one another, 
unless by supposing either great errors of observation, or great 
