EXCITATION OF ELECTRICITY. 
houses, or places for tea, coffee, &c. But 
private houses can only be searched upon 
oath of the suspicion before a commissioner 
or justice of peace, who can by their war- 
rant authorise a search. The office of ex- 
cise has also several excellent regulations 
for procuring the due attention and good 
conduct of their officers. 
EXCITATION of electricity. When a 
non-conductor of electricity is brought into 
an electrified state by any other means 
than that of direct communication with 
some other electrified body, it is said to be 
excited ; and this term is also applied to de- 
note the like production of an electric state, 
even in bodies which conduct. The pro- 
cesses by which excitation is performed are 
very imperfectly understood. It is proba- 
ble that they will all be hereafter found to 
consist in the same act ; and that this will 
principally be governed by changes in the 
combination, and perhaps the temperature 
of bodies. 
1. The electric state is produced in va- 
rious bodies by heating or cooling, particu- 
larly in the tourmalin. Sulphur, chocolate, 
and various other substances become elec- 
trified upon congealing or becoming solid 
after fusion; and it is probable that this 
phenomenon would be found to be univer- 
sal, if proper means were adopted for as- 
certaining the electric states. Calomel, 
when it fixes by sublimation against the 
upper surface of a glass vessel, frequently 
breaks through by an electric explosion. 
The glacial phosphoric acid was observed 
by Chaptal to emit strong electric sparks, 
while congealing. AVater and other fluids 
become electric by evaporation. And the 
chemical changes of bodies have been 
shewn in numerous galvanic experiments, 
to be attended with corresponding changes 
of electricity. See Galvanism. 
2. The mechanical action of bodies upon 
each other produce electrical effects. If 
two metals or other conductors be brought 
into contact, and separated, or if they be 
pressed or rubbed together, electric signs 
are produced ; and the same consequences 
follow, if one or both the bodies be non- 
conductors : but the electricity is more ma- 
nifest where the non conducting property 
prevails. When non-conductors are broken 
or torn asunder, the surfaces which were 
before in contact are found to be in op- 
posite electric states ; and this difference is 
so considerable in Muscovy talc, that bright 
sparks pass between them. From these 
facts, there is ground to suspect, that the op- 
posite electric states prevail amongst the 
parts of bodies, and may perhaps be in 
some manner concerned in the general at- 
traction they exert upon each other. 
3. The electricity in our common ma- 
chines is produced by the friction of a con- 
ducting body against anon-conductor. See 
Machine, electric. 
The non-conductor may be a tube, a 
globe, a cylinder, or a plate of glass, and the 
conducting rubber is usually a cushion upon 
which a mixture of the amalgam of zinc, 
with a little tallow has been smeared. It is 
found to be a condition, that atmospheric 
air should be present ; and if the electri- 
city be taken off from the surface of the cy- 
linder while it revolves, the cushion will not 
restore or supply the electric state, unless 
it be admitted to communicate with the 
earth. So that if an insulated conductor be 
placed near the cylinder, it will receive 
electricity for a time, though the rubber be 
also insulated ; but the rubber itself, after 
assuming the negative state, will soon cease 
to give any more electricity to the cylinder, 
than the little it may obtain from the im- 
perfect nature of its insulation. But if a 
communicating branch from the positive 
conductor be brought within a short dis- 
tance of the negative cushion, the positive / 
sparks will fly through the interval, and 
supply the cushion ; and in this manner the 
circulation of electricity may, as far as yet 
has been determined by experiment, be 
kept up for an unlimited time. It seems, 
therefore, as if a chemical process requiring 
atmospheric air, and therefore of the nature 
of combustion, were carried on at the face 
of the cushion, and that a peculiar substance 
on which the electric state depends, be- 
comes deposited or disposed in a different 
manner from that which it possessed be- 
fore ; and that the relative motion of the 
non-conducting body carried it off to a si- 
tuation where it tends to its former state, 
and consequently advances in a current to- 
wards such parts as allow of the restoration 
of that state. It seems reasonable to con- 
clude, that the disturbances of the electric 
state or equilibrium, and the currents by 
which they are restored, are in most natu- 
ral operations performed through very short 
and good conductors ; so that though in all 
probability they may contribute to very im- 
portant results, the immediate changes elude 
our observation, except in a few instances, 
such as that of lightning and luminous me- 
teors. And it seems from the facts to be 
nearly decided, that we should never have 
