The Republican. [volume] (Oakland, Md.) 1877-current, 1883-01-06
DeceptiOns Of Touch.


Immerse the forefnger of one hand
In water at 104 degrees Fahrenheit,
and then plunge the whole of the
other hand into water with temper
ature of102 degrees Fahrenheit. TIE
latter although two degrees cool.
er, will be judged to be the
warmer of the two, from which
it appears that the intensity of the
sensation of temperature depends
not only upon the relative degree of
heat to which the parts are exposed
but also upon the extent of surface
over which it is applied. From this
cause bath which is not uncomfort-
ably warm, when few fingers are
dipped in it, appears scalding hot
when the whole body is immersed.
The sense of temperature is, like
wise. entirely at fault when required
to determine which is the warmer of
two substances, say piece of iron
and piece of wood, for if they both
have the same temperature, the iron
will feel the hotter of the two, be.
cause of its being a so much better
conductor. A slight difference of
temperature, however, between two
substances of like nature is easily dis.
cerned, and we may here describe
simple but highly entertaining trick
which is founded on the fact.
The performer. having placed his
hat behind him, requests the people
present to place in it three or four
pennies. He shakes it up behind
him, and then asks some person to
take out penny and closely examine
it. He has then to pass it to the
others for examination, the last one
pitching it back into the hat again.
The pennies PIE then reshaken up.
and the performer now, placing one
hand behind him. picks out the PEN
ny which has been examined, al
through throughout the whole oper-
alton he has never seen it. When
the experiment has been done some
two or three times successfully, all
sorts of unlike suggestions are made
as to the way in which the feat has
been performed, but very seldom the
right one, which is exceedingly sim-
pie. The people,. in handling the
penny which was selected from the
others, make it warm. 1t is there
fore. easy to pick it out from the
others when it has been pitched into
the hat again. This sufficiently dem
onstrates the fact that at ordinary
temperature the sense of temperature
as localized in the fingers is sufficient
ly sensitive to discriminate between
several pieces of metal SO as to say
which is the warmest.
But for the extremes of hot and cold,
touch is thoroughly deceived, a piece
of frozen mercury giving a burning
sensation like a red-hot bar of metal.
The touch which attains to such per-
lection in persons afflicted with blind
ness is readily deceived. This is
shown forcibly by the experiment OF
Aristotle. Cross the index and mid
die fingers and run them over mar
BILE placed on the table with the eyes
shut. Under such circumstances one
has difficulty in avoiding the belief
that he is dealing with two marbles
instead of one. The idea of round
ness which has been obtained by a
complex judgment, founded on the
coalescence of several sensations, Is
here appealed to. but the usual con-
ditions being reversed, we draw
wrong conclusion. The sense of taste
may likewise be confounded by alter
ing the conditions under which the
gustatory operation is always carried
on. Thus, if the nostrils be held
firmly, it is impossible to distinguish
between applying an onion or an
apple to the tongue. Science for AU.
i u t.. -