603 
ELECTRICITY. 
when they perceive their approach, they fre- 
quently endeavour to break them by tiring 
a cannon before they approach too near the 
ship. They have also been known to have 
committed great devastations by land: 
though, where there is no water near, they 
generally assume the harmless form of a 
whirlwind. Sec Waterspout, and Me- 
teorology. 
In accounting for these phenomena upon 
electrical principles, it is observed, that the 
affluent matter proceeds from a body actu- 
ally electrified, towards one which is not so ; 
and the abluent matter proceeds from a 
body not electrified, towards one which 
is actually so. These two currents occasion 
two motions analogous to the electrical at- 
traction and repulsion, If the current of the 
-effluent matter is more powerful than of the 
affluent matter, which in this case is com- 
posed of particles exhaled from the earth, 
the particles of vapours, .which compose the 
cloud, are attracted by this effluent matter, 
and form the cylindrical column called the 
descending water-spout ; if, on the contrary, 
the affluent matter is the strongest, it attracts 
.a sufficient quantity of aqueous particles to 
form gradually into a cloud, and this is com- 
monly termed the ascending water-spout. 
Of the electricity zvhich is produced by 
inruns of melting, heating, cooling, and 
evaporation . — If sulphur is melted in an 
earthen vessel, and the whole is left to cool 
•upon conductors ; and if afterwards the sul- 
phur, when cold, is taken out of the vessel, 
it will be found strongly electrical ; but not 
at all so if it is left to cool upon electrics. 
If sulphur is melted in a glass vessel, and 
is left to cool, both the glass and the sulphur 
will acquire a strong electricity, the former 
positive and the latter negative ; and that 
will be the case whether they are left to cool 
upon electrics or upon conductors. 
If melted sulphur is poured into a vessel 
of baked wood, it will acquire the negative, 
.and the wood the positive, electricity ; but 
if it is poured into sulphur, or rough glass, 
it will acquire no sensible degree of elec- 
tricity. 
Melted sulphur poured into a metal cup, 
and there left to cool, shews no signs of elec- 
tricity whilst standing in the cup ; but if 
they are separated, then they will both 
appear strongly electrified, the sulphur posi- 
tive, and the cup negative. If the sulphur is 
replaced in the cup, every sign of electricity 
will vanish; but if, whilst separate, the elec- 
tricity either of the cup or sulphur is taken 
off, then on being replaced they both will 
appear possessed of that electricity which has 
jiot been taken off. 
Melted wax, being poured into glass or 
wood, acquires the negative electricity, and 
the glass or wood becomes positive. But 
sealing-wax, poured into a sulphur vessel, 
acquires the positive electricity, and leaves 
the sulphur negative. 
Chocolate fresh from the mill, as it cools 
in the tin pans in which it is received, be- 
comes strongly electrical. When turned 
out of the pans, it retains this property dur- 
ing a certain time, but loses it presently by 
handling. By melting it again in an iron 
ladle, and pouring it into the tin pans as at 
first, you may renew its power once or twice ; 
but w hen the mass becomes very dry and 
powdery in the ladle, the electricity is no 
longer revived bv simple melting; but if then 
a little olive oil is added, and is mixed well 
with the chocolate in the ladle, and is after- 
wards poured into the tin pans as at first, 
it will be found to have completely recovered 
its electrical power, which continues a con- 
siderable time. 
The property of becoming electrified mere- 
ly by heating or cooling, was first observed 
in, and is eminently possessed by, a hard 
pellucid stone called the tourmalin, which is 
generally of a deep red, or purple, or brown 
colour ; which seldom, if ever, exceeds the 
size ot a small walnut; and which is found in 
several parts of the East Indies, especially 
in the island of Ceylon ; but on farther ex- 
amination it has been found that several 
other precious stones, and especially the 
Brasilian emerald, possess the like properties 
more or less ; hence\ the following particu- 
lars, which have been principally observed 
of the tourmalin, must be understood 
to belong likewise to most other precious 
stones, 
1. The tourmalin, while kept in the same 
temperature, shews no signs of electricity ; 
but it will become electrical by increasing or 
diminishing its heat, and stronger in the lat- 
ter circumstance than in the former. A very 
trifling alteration of temperature is often suf- 
ficient to produce the effect. 
2. Its electricity does tint appear all over 
its surface, but only on two opposite sides 
of it, which may be called its poles, and 
which always are in one right line with the 
centre of the stone, and in the direction of 
its strata; in which direction the stone is 
absolutely opaque, though in the other it is 
semitransparent. 
3. Whilst the tourmalin is heating, one of 
its sides (call it A) is electrified plus, or posi- 
tive, and the other B minus; but when cool- 
ing, A is minus, and B is plus. Hence, if 
one side of the stone is heating, whilst the 
other is cooling, then both sides will acquire 
the same electricity ; or if one side only 
changes its temperature, then that side 
only will appear electrified. 
4. If this stone is heated, and suffered to 
cool without either of its sides being touched, 
then A will appear positive, and B negative, 
all the time oi its heating and cooling. 
5. This stone may be excited by means 
of friction like any other electric ; and either 
of its sides, or both, may be rendered posi- 
tive. 
6. If the tourmalin is heated or cooled 
upon some other insulated body, that body 
will be found electrified as well as the stone; 
but it will be found possessed of the elec- 
tricity contrary to that of the contiguous 
side of the stone. 
7. The electricity of either side, or of both, 
may be reversed by heating or cooling the 
tourmalin in contact with various substances, 
such as the palm of the hand, a piece of 
metal, &c. 
S. These properties of the tourmalin are 
also observable in vacuo, but not so strong 
as in the open air. 
9- If a tourmalin is cut into several parts, 
each piece will have its positive and negative 
poles, corresponding to tiie positive and nega- 
tive sides of the original stone. 
10. If this stone is covered all over with 
some electric substance, such as sealing-wax. 
oil, &c. it will in general shew the same pro- 
perties as without it. 
11. A vivid light appears upon the tour- 
malin, whilst heating in the dark, and by a 
little attention one may be easily enabled by 
this light to distinguish which side of [lie 
stone is positive, and whic h negative. Some- 
times when the stone is strongly excited, 
pretty strong flashes may be seen in the dark, 
to go from the positive to the negative side 
of it. 
\2. Lastly, it has been found that with 
respect to the electric properties, the tour- 
malin is sometimes injured by the action of 
a strong lire, at other times is improved, 
and sometimes is not at all altered by it. 
The evaporation of water, as also of some 
other fluids, produces electricity, viz. those 
bodies from which the water has departed, 
will remain in a negative state of electricity, 
indicating that the water by its conversion 
into vapour has its capacity for the electric 
fluid increased, as it has its capacity increased 
for containing heat. But though the effect 
is in general such as has been mentioned 
above, yet there are two exceptions which 
involve the subject in some difficulty, and 
which will require farther experiments and 
consideration. 
The exceptions are, 1st, that if water is 
evaporated by being put in contact with a 
red-hot piece or pieces of very rusty iron, 
it will leave the iron electrified positively ; 
whereas, if the iron is not rusty, the evapo- 
ration of the water from its surface will leave 
it electrified negatively. 2dly. If water is 
evaporated by throwing into it impure red- 
hot glass (such as the green glass of common 
bottles), the vessel, or the remaining water, 
will be electrified positively. 
This curious production of electricity by 
evaporation, as also the production of elec- 
tricity by the condensation of vapour, may 
be easily observed in the following man- 
ner : 
Place a metallic cup, or a pewter plate, 
upon an insulating stand, and connect a sen- 
sible electrometer (fig. 18) with it. Also 
place one or two lighted coals in the cup 
or plate; then pour a little water at once 
upon the coal or coals, which will produce 
a quick evaporation accompanied with a 
great hissing noise, and at the same time 
the electrometer will diverge with negative 
electricity. 
If the steam which issues copiously' from 
water quickly boiling, is received under a 
pretty large and insulated metallic plate, 
that plate, by the condensation of the steam 
upon it, will be electrified positively, as 
may be ascertained merely by connecting a 
sensible electrometer with it. 
On throwing a variety of other substance's 
upon actually burning, or only hot and in- 
sulated coals, the coals, Ac. either shewed 
negative electricity, or no electricity at all. 
Either spirit of wine, or ether, when thus 
treated, left the coals negative; but if (the 
coals being sufficiently hot) the spirit of wine 
or the ether took lire, and burned in their 
usual way, then no electricity was pro- 
duced. 
Of animal electricity .— nder this title 
we shall take notice of that electricity only 
which is produced from the animal itself, in 
consequence of its particular organization, 
and not that which* is produced by the ap- 
