1817.) on the Intensity and Nature of Electricity. $55 
Sulphur and sealing-wax are a little less difficult than glass to 
feel the impression of cold. Paper and cotton, silk and linen, are 
more so. 
Cold then produces and developes the electric power of all bodies; 
but its influence is not the same for all bodies. 
Second Fact.—1. If we plunge a glass rod into mercury during 
winter, and when it is cold into mercury of the temperature of 32°, 
it comes out at first much more electric than from mercury of the 
temperature of the room. If we continue the immersions, we per- 
ceive it as it gets cold become more weakly electric, and some time 
after to become quite inexcitable. It is in vain, then, to continue 
the immersions ; its electricity does not again appear. It refuses 
equally to become electric when rubbed with flannel. If we allow 
the mercury and the glass to recover their temperature, the rod gra- 
dually recovers its power; and, what is remarkable, when both 
have recovered the temperature of the chamber, the rod is found to 
be more electric than before the cooling. 
When the electric power is strongly developed, the rod does not 
lose its energy when plunged into mercury of the temperature 32° 
till after it has remained 62”, Only 30” are required when the 
electric tension is not so strong. 
2. The electric power of sulphur and sealing-wax is rather more 
difficultly destroyed than that of glass by the action of cold. ‘That 
of silk and of wool is still more so, On Jan. 24, 1814, during a 
cold north-east wind, wool did not cease to be electric in mercury 
of 23° till after 20 immersions, remaining 30” in the mercury at 
each; that is to say, at the end of six minutes. Eight minutes 
were requisite for silk, 45” for sealing-wax, 30” for sulphur, and 
15” for glass. The electric power of wool cannot be destroyed in 
mercury of the temperature 26°5°, while that of glass may be de- 
stroyed in mercury of the temperature of 43°. 
It is remarkable that when glass, sulphur, and sealing-wax, are 
on the point of losing their energy in cold mercury, they begin to 
be inexcitable at the bottom of the rod before they are so at the 
top; while silk and wool lose their energy at the top of the cylinder 
before they do so at the bottom. 
3. If we put a vessel full of mercury into a frigorific mixture of 
the temperature 23°, and plunge a rod of glass into it at intervals 
so distant that it may preserve the temperature of the apartment, it 
comes out for a long time very electric. At the end of about three 
quarters of an hour its electricity begins to get weak, Some time 
after the rod becomes inexcitable ; though after coming out of that 
it is always very electric in mercury of the temperature of the 
room. When the electric tension is very strong, the mercury re- ° 
quires to be cooled down to 14° or 101° before the rod loses its ex- 
eitability. When the mereury at this degree of cold is no longer 
capable of exciting the glass, it is still capable of exciting silk and 
wool. 
In summer, when the mean temperature of the air is high, mer- 
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