Evening star. [volume] (Washington, D.C.) 1854-1972, 1890-04-01
THE LAW OF CHANCE.
The Result Of Some Of Prof. Nenden.
halls Experiments.

u
halls Experiments.
HIS TALK ON CHANCE AND THE LONG RUS-aAM-
BLING A POOR OCCUPATION FROM A BUSINESS
sTANDPorNT-THE CREDIBILrrY OF TESTIMONY
THE CHARACTERISTIC CURVE" OF AUTHOR.
Very much interested was the audience that
listened to Prof. 7. c. Mendenhall Of the Geo
logical Survey as he lectured on Saturday after
noon at the National Museum on 'Chance and
the long run"
In the beginning Prof. Mendenhall referred
briefly to the history of the doctrine of chance
or the law of probability. saying that it had its
real origin in the work OF Pascal, who abou.
the year 1854 was called upon to decide dis
puse between two gamblers. From the time of
Pascal to the present the subject had received
the consideration of the ablest mathematician,
including especially the grea. La Place, and
nearly every great mathematical scholar had
contributed to its growth.
lie then proceeded to show that the probable
lty, or chance, or facility" Of an event might be
expressed automatically by means of frac-
tlon- When the value of this fraction was one
the event was certain to happen. References
were made, IN illustration, to the tossing of
coins. throwing dice, drawing balls from jars,
DC. 1t is possible to calculate the probability
OF some very complex events and the processes
involve the use OF very difficult mathematical
methods. 1t was, therefore, desirable to verify
the result of this mathematical treatment of
the subject by means of experiment Several
experimental tests of the principles Of the doc
trlne OF chance were described. 1t was posi-
BILE to calculate the probability that a short
SUCK IN falling on surface ruled with parallel
lines would or would not lie across one of those
lines. Having computed this probability Prof.
Mendenhall said that he had verified the result
DlfCnlnO rph a gIlrtlcQ
noting how it fell twenty thousand times. This
Is probably the most extensive experimental
test ever applied. The numerous applications
OF the laws OF chance were next referred to.
THE CREDIBILITY OF TESTIMONY.
Especial attention was given to its use in
expressing the credibility Of human testimony
and determining its weight. If the credibility
OF a man was expressed by the fraction four
ffths it meant that what he said would, in the
long run, be true four times out of five. Rea-
sons were given for believing that the average
credibility was about three-fourths, in which
was included not only any tendency to lie
which might exist but also the chances OF
being mistaken. 1t was stated that if the cred
Utility of witnesses was one-half one witness
was as good as a hundred; il it was less than
one-half the fewer such witnesses called the
better, and If more than one-half additional
testimony would strengthen the evidence. Some
of the fallacies OF gam blers were referred to
and illustrations were given to show their alb
surdity. 1t was shown that games of chance
lndulged in for gain were bad from business
standpoint IL from no other, rs in any case
the loss was greater than the gain.
DETECTING AUTHORSHIP.
An application of the laws of ''chance and
the long run" was made in proposed plan for
detecting authorship by sort OF word analy-
sis. Tho method depends on two or three as
sumptions.
The nature of the process, the speaker said,
Is extremely simple, but it may be useful to
point out Its similarity to a well-known method
of material analy sIs, the consideration of which
actually first suggested to the writer its literary
analogue.
BY the use of the spectroscope beam of nom
homogeneous light is analysed and its COM
ponents assorted according to their wave
length. As is well known, each element when
intensely heated under proper conditions
sends forth light which. upon prismatic
analysis. is found to consist of groups of waves
of definite length and appearing in certain
definite proportions. So certain and uniform
are the results of this analysis that the appear
ance of particular spectrum is Indisputabe
evidence of the presence of the clement to
which 1t belongs.
AN AUTHORS "CURvE."
In a manner very similar it is proposed to
analyze a composition by forming what may
be called a "word-spectrum," or characteristic
curve" which shall be a graphic representa-
ton Of an arrangement of words according to
thelf length and to the relative frequency of
their occurrence. If. now. it shall be found that
with every author, as with every element, this
spectrum persists in its form and appearance.
the value Of the method will be at once con-
coded. 1t has been proved that the spectrum
of hydrogen is the same whether that element
Is obtained from the water of the ocean or from
the yapor of the atmosphere. Wherever and
whenever II appears it means hydrogen. If
it can be proved that the word-spectrum or
Characteristic curve exhibited by an analysis of
David Coppertield' is identical with that of
"Oliver Twist" of 'Barnaby Rudge." of Great
Expectations" of the '.Child's History of Eng
land" &C.. and that it differs scnsibly from
that of VANITY Fair" or Eugene Aram," or
Robinson Crusoe." or Don Quixote," or any,
thing elsa IN fact, then the conclusion will be
tolerably certain that when it appears it means
Dickens.
The validity of the method as a test of
authorship, then. implies the following assump-
tions: That every writer makes use of a vo-
cabulary which is peculiar to himself and the
character of which does not materially change
from year to year during his productive period;
that, in the use of that vocabulary in compost
ton, personal peculiarities in the construction
of sentences will, in the long run, recur with
such regularity that short words, long words
and words of medium length will occur with
definite relative frequencies.
Prof. Mendenhall suggested that the method
was capable of application to the celebrated
Shakespearan-Bacon problem. and he yentured
TO assert that If 1t were correctly used it would
not fail to settle this question.
The authorship of the letters of JunIus nigh.
also be determined by this interesting process.
AN IMMENSE UNDERTAEISc