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though some conduct it with much more fa- 
cility than others. 
M hen electricity became a science, so far 
as to attract the notice of philosophers, va- 
rious modes were employed for producing 
or accumulating the electrical matter. 
The first electrical machine made use of 
was a tube of glass, which, being excited bv 
friction, was then put in a state to communi- 
cate electricity to other bodies. The best 
glass for this purpose is the line white Eng- 
lish crystal. The most convenient dimen- 
sions for these tubes are about three feet in 
length, twelve or fifteen lines in diameter, 
and the glass quite a line in thickness. It is 
ol iittle importance whether the tube is open 
or closed at the extremities; yet it is neces- 
sary that the air within should be in the same 
state as that without : for this reason the tube 
should at least be open at one end; hut care 
must be taken that dust should not be ad- 
mitted into the inside, for that would consi- 
derably impede its effects. If, notwithstand- 
ing these precautions, the tube receives ei- 
ther dust or moisture, some dry and line 
sand should be introduced into the inside, and 
it should be afterwards cleaned out with tine 
dry cotton. 
hen it is intended to electrify a tube, it 
is only necessary to take the end in one hand, 
and to continue to rub the tube with the 
other hand, from one end to the other, until 
it affords marks of its being sufficiently char- 
ged with the electric fluid. 'This friction may 
be performed with the naked hand when il is 
dry and clean, otherwise with a piece of soft 
brown paper, or waxed taffeta. When the 
tube has been rubbed in this manner, the 
c ircumambient air being dry, if light sub- 
stances are presented to it, they will be first 
attracted towards it, and immediately after- 
wards repelled. 
The electric fluid may be excited in nearly 
a similar manner, by rubbing a stick of sul- 
phur or sealing-wax. 
These tubes being but small, the quantify 
of electricity produced is but feeble in its 
effects. We have seen that a method was 
contrived to turn a globe of glass upon its 
axis by means of a machine with a winch or 
multiplying wheel : this method admitted of 
a larger surface, and the friction was perform- 
ed with greater ease, by means of a rubber 
bring placed close to the revolving globe, 
'fhe electrifying machine has however since 
undergone various improvements, and per- 
haps is capable of still more. 
In the plate, fig. 1. is a representation of 
an electrical machine with a prune conduc- 
tor. ABC represents the bottom board of 
the machine, 1) and E the two perpendicu- 
lar supports which sustain the glass cylinder 
EG. The axis of the cap K passes through 
the support !); on the extremit - of this axis 
a simple winch L is fixed. The axis of the 
other cap runs in a small hole, which is made 
in the top of the supporter E. 
P is the glass pillar to which the cushion is 
fixed ; T a brass screw at the bottom of this 
pillar, which is to regulate the pressure of 
the cushion against the cylinder. This ad- 
justing screw is peculiarly advantageous : bv 
it the operator is enabled to lessen or increase 
gradually the pressure of the cushion, which 
it effects in a much neater manner than it is 
possible to do when the insulating pillar is 
sixed on a sliding-board. 
ELECTRICITY. 
Y represents the positive prime conductor, 
or that which takes the electric fluid imme- 
diately from the cylinder; M the glass pillar 
by which it is supported and insulated; and 
X a wooden foot or base for the glass piliar. 
Fig. 2. is a plate-glass machine, of the most 
portable construction, with a double Leyden 
phial made square to suit the base, which an- 
swers all the purposes of medical electricity. 
ABC is a wooden frame to which the four 
rubbers are affixed, and by means of screws 
may be made to bear with proper pres- 
sure on the circular glass plate DF; titis 
plate has a hole through its middle, to which 
an axis is firmly fixed, and it is turned by the 
winch L; CG is a Leyden phial (with the 
collectors oo fixed on the top) fixed in a 
larger one 1 1 : when a strong shock is wanted, 
the long pin 1 is let in to touch the bottom, 
by which means the large jar acts; but when 
drawn out, the small one acts alone but much 
quicker, from being inclosed in the other. 
K is the electrometer. When this machine 
is constructed on a large scale for experi- 
ments, a prime conductor M, fig. 4, may he 
attached to the wooden frame opposite thy 
axis of the plate-glass instead of the jar. Fig. 
3 is a side view of the machine, with a clamp 
X to fix it to the table when used. 
ihe advantages of this machine are, that it 
may be made portable, and is of so simple a 
construction, that any gentleman in the coun- 
try, after procuring a plate of a reasonable 
thickness from a glass-house, may, by the aid 
of a common cabinet-maker, construct one 
tor his own use; the conductor may be equally 
insulated by rosin, wax, silk, or any other 
electric or non-conducting substance. 
When of a large diameter, these plate ma- 
chines are by far the most powerful of any ; 
and this power is greatly increased by a se- 
cond plate parallel to the other, and turning 
on the same axis. The most powerful ma- 
chine of which we have ever heard is one 
made in this country for the museum of 
leylar, at Harlem. It consists of two circu- 
lar plates of five feet five inches diameter. 
1 he plates are about 7\ inches asunder, and 
each is excited by four rubbers. The prime 
conductor is divided into two branches which 
enter between the plates, and by means of 
points collect the electrical fluid. These 
'plate machines, however, with two plates, are 
turned with great labour, and are liable to 
nune accidents when large than the common 
cylinders. 
Previous to the consideration of these cir- 
cumstances, by which a large quantity of the 
electric fluid may be executed, it mav be ne- 
cessary to premise, that the resistance of the 
air seems to be lessened where the cushion 
is in close contact with the cylinder; and 
that the electric matter, agreeable to the- law 
observed by all other elastic fluids, is pressed 
towards that part where it finds least resist- 
ance; the same instant, therefore, that the 
cylinder is separated from the cushion, the 
lire issues forth in abundance, because the 
resistance made to it by the action of the at- 
mosphere is lessened at that part, 'i he more 
perfect the continuity is made, the greater is 
the quantity of electricity which will proceed 
from the cushion. 
To excite, therefore, an electrical machine 
effectually, it is necessary first to discover i 
those parts of the cushion which are pressed ; 
by the glass cylinder, and then the amalgam 
must be applied to those parts onlv. The 
line of contact between the cylinder and 
cushion must be made as perfect” as possible, 
and the fire which is collected mint be pre- 
vented from escaping, The breadth of the 
cushion should not be great, and it should lie 
placed in such a manner that it may be easily- 
raised or lowered. 
In order to find the line of contact between 
the cylinder and cushion, place a line of w hit- 
ing which has been dissolved in spirit of wine, 
on the cylinder: on turning this round, the 
whiting is deposited on the cushion, and 
marks those parts -of it which bear or rub 
against the cylinder. The amalgam is to be 
put on those parts only which are thus mark- 
ed by the whiting. 
"Whenever the electricity of the cylinder, 
grows less powerful, it is easily renewed by 
turning back the silk which lies over it, and 
then rubbing the cylinder with the amalga- 
mated leather, or by altering the pressure of 
the adjusting screw.” 
A small quantity of tallow placed over the 
amalgam is observed to give more force to 
the electric powers of the cylinder ; or the 
same end may be effected by rubbing the cy- 
linder with a coarse cloth, which has been" a 
little greased, and afterwards wiping il with a 
clean cloth. 
As air not only resists the emission of the 
electric fluid, but also dissipates what is col- 
lected, on account of the conducting sub- 
stances which are floating in it, over the cy- 
linder a piece of black or oiled silk should be 
placed, from the line of contact to the collect- 
ing points of the prime conductor, and these 
points should be placed within its atmo- 
sphere. 
Sometimes (lie silk will adhere so strongly 
to the cylinder, when zinc amalgam is used, 
as to render it very difficult to turn; but this 
may be obviated by rubbing a sma’l quan- 
tity of aurum musivum, or a little whiting, 
over the silk, when it is w iped clean. 
The following directions of Mr. Adams, 
relative to exciting the machine, will be use- 
ful to the experimentalist: 
“ To excite your machine, clean the cy- 
linder, and wipe the silk. 
“ Grease the cylinder by turning it against 
a greasy leather, till it is uniformly obscured. 
The tallow of a candle may be used. 
“ Turn the cylinder till the silk flap has 
w iped off so much of the grease as to render 
it semi-transparent. 
“ Put some amalgam on a piece of leather, 
and spread it well, so that it may he uniform- 
ly bright: japply this against the turning cy- 
linder, the friction will immediately increase, 
and the leather must not be removed until it 
ceases to become greater. 
“ Remove the leather, and the action of 
the machine will be verv strong. 
u 1 he pressure of the cushion cannot lie 
too small, when the excitation is properly 
made.” 
There are now in use two kinds of amal- 
gam: one is made of quicksilver five parts, 
due one part, which are melted together 
y it h a small quantity of bees-wax ; the other 
s the aurum musivum of the shops, w hich is 
in and sulphur. Before either of these will 
idhcre closely to the silk it is necessary to 
