Public ledger. [volume] (Memphis, Tenn.) 1865-1893, 1876-05-10
now Qulek ia Thoughtq ?

In order to express an idea of ex-
ceeding rapidity we say "as quick as
thought" 1t seems evident, how
ever, since thought cannot be spon-
taneous, but must arise from some
cause, the latter preceding the for
mer, that there must be some ap-
preciable duration of time elapsing
between the two, which might be
called "the period Of succession"
1t is quite amusing to recall the
fact that, in 1895, at the Greenwich
Observatory, an irate astronomer
summarily dismissed an assistant
because he always made an appar-
ent blunder in noting the passage
of a star, which showed an error of
five to eight-tenths of a second. A
quarter of a century afterwards the
astronomer Bessel found errors of a
smaller kind, made by two illus
trious assistants who were working
with him, Argelander and Sturve,
and instead of soundly rating them
for their apparent blunders, com
menced studying the subject, and
was the first to present what is
called the problem of "the personal
equation" The personal equation
is, then, a certain fixed human
error, that difference between the
time when something actually does
take place, and when the apprecia-
ton of it reaches our brain. NJ.
Wolf, of the Paris Observatory, has
devoted a great deal of time to the
study Of this curious subject, and
has invented some ingenious mech.
anism for the determination of it,
| A luminous point-an artificial stal
| as it were-is passed before the
field of the glass, and its exact time
being calculated, by means Of a
most accurate chronometer, be.
tween the actual time it does ap
pear, and that noted by an observer,
may be called one Of the limits Of
! the visual personal equation, This
equation, of course, cannot be con
slant. 1t may vary as to the kind
of impression, and may differ with
individuals.
Between Bessel and Argelander
when the two would note the time
Of a flash Of lightning, there would
be a difference of twenty-five one,
| hundredths of a second. The
errors of both these observers be-
tween actual occurrences and the
precise time when the passage of 3
star was noted, were as much as 6
quarter Of a second. Summing III
these errors, the period when W.
are conscious of receiving an i'm
preston shows us to be as much
out of the way az from the fifth tC
the tenth of a second. Again, The
effect or the impression of its dis,
tinguishing character acts on u
| differently. Another term is EN-
ployed for this personal equation
which is called physiological time
Now this time varies with the va
rious sense, and whether the effect
are single or double. The physio
logical time for a single sound j
15S-l000 Of q second, but whel
two sounds are received it i
203-1000 of a second. Of coursei
is evident that, when there is tn
expectancy of any known effect
such as Of light, sound, or touch
the mind being prepared for som
impression, the physiological tim
is very much lessened, One yer
curious portion of this study woul
be that Of discovering whether moo
Iification in the human brain
brought on by medicines or. disease
did not cause differences in thi
y physiological time. DO the insan
have quicker or slower physiolog
a cal time? When De Quincey a
serted that to live thousand year
: in a single night was quite possibl
by simply increasing his dose
opium, he inadvertently touched o
the problem of physiological tim,