The news and herald. (Winnsboro, S.C.) 1877-1900, 1883-05-03
ilysics Nitltut AlIxlat,s.
During a lecture course bv professo,

| ------------
| During lecture course by professors
who have at their disposal complete
set of physical apparatus, there are
some experiments performed by them
which at first sight seem very complicat-
ed but which nevertheless may be re-
peated by means OF very simple objects.
! There is, for instance, the interesting
Lissajous experiment.. which consists,
as the reader is perhaps aware, in throw
ing on screen, by means of the oxyhy-
drogen lamp. the curves traced by one
OF the arms Of a tuning fork in sonor.
Gus vibration. An analogous expert
ment may be exhibited by means of q
common knitting needle. Fix one Of the
| extremities of the needle3 in cork to
servo as base; then to thetS upper free
| extremity attach a ball ob sealing wax,
and on this gum small circle Of paper
| about the diameter of pea, Now,
holding the cork firmly between the
| finger OF the'left hand, cause the needle
to sharply vibrate, either by bending it
far to one side and then suddenly releas-
ing 1t, Oh by striking it smartly with o.
| wooden ruler. The little ball of wax
surmounted by paper will be seen to des-
cribo morelor less elongated ellipse, or
( circle, according to the intensity or
the number Of vibrations. The phenom-
enon is very perceptible, when cnre is
taken to cause the needle to vibrate
under strong light from a lamp; and,
in such case the persistence of the i'm
preston on the retlna causes tho vibra-
| ting wire to form an image which has
tho appearance Of long and graceful
bouquet holder, or champagne glass.
Among the experiments sometimes
performed to demonstrate molecular at
fractions, there is one which is execut-
cd by means of al apparatus of pecuI-
lar structure but the sumo phenomenon
may be shown III a much more simple
manner, as follows: Having cut two small
spheres ont OF bottle cork, place them
Oh the surface Of water. If one of tho
balls now be carefully pushed along un-
til 1t is III quite close proximity to the
other, the two will be seen to quickly
rush towards each other, just as a bit Of
iron flies to magnet when the latter is
brought near it.
A writer has pointed out neat meth
cd OF obtaining an electric spark by
means of simple apparatus which he
calls the ''tea-tray electrophorus. A
common metallic tea tray is supported
on two dry glass goblets. A piece of
common brown paper, cut so as to be a
little smaller than the tray, and with
round corners is warmed, laid on the
table and rubbed briskly with piece
OF lndla-rubber, or with clothes brush
1t is then laid down for an instant on
the tray. Ii at this juncture some per-
son presents his knuckle to the tray he
favorable plight spats:a Gay hs @
OF inches long. BY simply putting the
paper down, touching the tray, and
again lifting up the paper, the tray is
again charged, and large number Of
sparks may be thus drawn ono after the
other i'll rapid succession. The paper
may be lifted by the hands. but it will
be found better If couple of strips of
paper be fixed on with wax TO servo as
handles
The sparks obtained by the tea-tray
electrophorus may produce slight
pricking sensation, but to give regular
electric shock will obligo us to store ur
charge ILL Leyden jar. This import
ant piece Of apparatus may DO improvis. :.
ed as follows: A round. bottomed glass
tumbler is procured-thin glass is pre-
ferable-and is filled about three. quart
ers full of small leaden shot. Ii shot is
not at hand dry coal DUST will answer,
though not 80 we'll, and great caro- must
be taken to wipe clean the upper part of
the tumbler, Everything must be warm
ant. scrupulously dry. Into the shot is
inserted q silver spoon to serve tho
place of a rod and knob. The tumbler
is held by graspmg it we'll in the bottom
OF the haed, 80 that the palm may cover
the whole of the rounded bottom. Hav-
ing thus prepared and grasped the i'm
provised Leyden jar, it Is to be charged
with sparks from the tea tray electrop-
horus. It should be held with tho
spoon handle near to, but not touching
the edge of the ten tray, while another
person performs the operations OF lifting
the paper up and putting it down, then
touching the tray. then lifting up again
and SO on until q dozen ararEi have
been sent into the jar. On touching
the ''knob" q smart little Lock is OK
perienced in the wrists ani elbows. and
short, bright, swapping spark announ-
ces the discharge of the jar.