of muscular sense in any person, B, is twice as great as in that of
another person, A. It is that B is only capable of perceiving one
grade of difference where A can perceive two. We may, of course,
state the same fact inversely, and say that the delicacy of muscular
sense is in that case twice as great in A as in B. Similarly in all
other cases of the kind. Conversely, if having known nothing
previously about either A or B, we discover on trial that A can just
distinguish between two weights such as those bearing the
register-marks 5 and 7, and that B can just distinguish between
another pair, say, bearing the register-marks 2 and 6; then since
the difference between the marks in the latter case is twice as
great as in the former, we know that the dulness of the muscular
sense of B is exactly twice that of A. Their relative dulness, or if
we prefer to speak in inverse terms, and say their relative
sensitivity, is determined quite independently of the particular
pair of weights used in testing them.
It will be noted that the conversion of results obtained by the
use of one series of test-weights into what would have been given
by another series, is a piece of simple arithmetic, the fact
ultimately obtained by any apparatus of this kind being the "just
distinguishable" fraction of real weight. In my own apparatus the
unit of weight is 2 per cent.; that is, the register-mark 1 means 2
per cent.; but I introduce weights in the earlier part of the scale
that deal with half units; that is, with differences of 1 per cent.
In another apparatus the unit of weight might be 3 per cent., then
three grades of mine would be equal to two of the other, and mine
would be converted to that scale by multiplying them by 2/3. Thus
the results obtained by different apparatus are strictly comparable.
A sufficient number of test-weights must be used, or trials made, to
eliminate the influence of chance. It might perhaps be thought that
by using a series of only five weights, and requiring them to be
sorted into their proper order by the sense of touch alone, the
chance of accidental success would be too small to be worth
consideration. It might be said that there are 5 × 4 × 3 × 2, or 120
different ways in which five weights can be arranged, and as only
one is right, it must be 120 to 1 against a lucky hit. But this is
many fold too high an estimate, because the 119 possible mistakes
are by no means equally probable. When a person is tested, an
approximate value for his grade of sensitivity is rapidly found, and
the inquiry becomes narrowed to finding out whether he can surely
pass a particular mistake. He is little likely to make a mistake of
double the amount in question, and it is almost certain that he will
not make a mistake of treble the amount. In other words, he would
never be likely to put one of the test-weights more than one step
out of its proper place. If he had three weights to arrange in their
consecutive order, 1, 2, 3, there are 3×2 = 6 ways of arranging them;
of these, he would be liable to the errors of 1, 3, 2, and of 2, 1, 3,
but he would hardly be liable to such gross errors as 2, 3, 1, or 3,
2, 1, or 3, 1, 2. Therefore of the six permutations in which three
weights may be arranged three have to be dismissed from consideration,
leaving three cases only to be dealt with, of which two are wrong
and one is right. For the same reason there are only four reasonable
chances of error in arranging four weights, and only six in
arranging five weights, instead of the 119 that were originally
supposed. These are--
12354 13245 13254
21345 21354 21435
But exception might be taken to two even of these, namely, those
that appear in the third column, where 5 is found in juxtaposition
with 2 in the first case, and 4 with 1 in the second. So great a
difference between two adjacent weights would be almost sure to
attract the notice of the person who was being tested, and make him
dissatisfied with the arrangement. Considering all this, together
with the convenience of carriage and manipulation, I prefer to use
trays, each containing only three weights, the trials being made
three or four times in succession. In each trial there are three
possibilities and only one success, therefore in three trials the
probabilities against uniform success are as 27 to 1, and in four
trials at 81 to 1.
_Values of the Weights_.--After preparatory trials, I adopted 1000
grains as the value of _W_ and 1020 as that of _R_, but I am now
inclined to think that 1010 would have been better. I made the
weights by filling blank cartridges with shot, wool, and wads, so as
to distribute the weight equally, and I closed the cartridges with a
wad, turning the edges over it with the instrument well known to
sportsmen. I wrote the corresponding value of the index of _R_ on
the wad by which each of them was closed, to serve as a register
number. Thus the cartridge whose weight was _WR4_ was marked 4'. The
values were so selected that there should be as few varieties as
possible. There are thirty weights in all, but only ten varieties,
whose Register Numbers are respectively 0, 1, 2, 3, 3-1/2, 4-1/2, 5,
6, 7, 9, 12. The reason of this limitation of varieties was to
enable the weights to be interchanged whenever there became reason
to suspect that the eye had begun to recognise the appearance of any
one of them, and that the judgment might be influenced by that
recognition, and cease to be wholly guided by the sense of weight.
We are so accustomed to deal with concurrent impressions that it is
exceedingly difficult, even with the best intention of good faith,
to ignore the influence of any corroborative impression that may be
present. It is therefore right to take precautions against this
possible cause of inaccuracy. The most perfect way would be to drop
the weights, each in a little bag or sheath of light material, so
that the operatee could not see the weights, while the ratio between
the weights would not be sensibly changed by the additional weight
of the bags. I keep little bags for this purpose, inside the box
that holds the weights.
_Arrangement of the Weights_.--The weights are placed in sets of
threes, each set in a separate shallow tray, and the trays lie in
two rows in a box. Each tray bears the register-marks of each of the
weights it contains. It is also marked boldly with a Roman numeral
showing the difference between the register-marks of the adjacent
weights. This difference indicates the grade of sensitivity that the
weights in the tray are designed to test. Thus the tray containing
the weights _WR0_, _WR3_, _WR6_ is marked as in Fig. 1, and that
which contains _WR2_, _WR7_, _WR12_ is marked as in Fig. 2.
[Illustration: Fig. 1.]
[Illustration: Fig. 2.]
The following is the arrangement of the trays in the box. The
triplets they contain suffice for ordinary purposes.
|=========================================|
| Just | | |
| perceptible | Grade of | Sequences |
| Ratio. | Sensitivity | of Weights |
|-------------+-------------+-------------|
| 1.020 | I. | 1, 2, 3 |
| 1.030 | I.1/2 | 2, 3-1/2, 5 |
| 1.040 | II. | 3, 5, 7 |
| 1.050 | II.1/2 | 2, 4-1/2, 7 |
| 1.061 | III. | 0, 3, 6 |
| 1.071 | III.1/2 | 0, 3-1/2, 7 |
| 1.082 | IV. | 1, 5, 9 |
| 1.082 | IV.1/2 | 0, 4-1/2, 9 |
| 1.104 | V. | 2, 5, 7 |
| 1.127 | VI. | 0, 6, 12 |
|=========================================|
But it will be observed that sequences of 1/2 can also be obtained,
and again, that it is easy to select doublets of weights for coarser
tests, up to a maximum difference of XII., which may be useful in
cases of morbidly diminished sensitivity.
_Manipulation_.--A tray is taken out, the three weights that it
contains is shuffled by the operator who then passes them on to the
experimenter. The latter sits at ease with his hand in an
unconstrained position, and lifts the weights in turn between his
finger and thumb, the finger pressing against the top, the thumb
against the bottom of the cartridge. Guided by the touch alone, he
arranges them in the tray in what he conceives to be their proper
sequence; he then returns the tray to the operator, who notes the
result, the operator then reshuffles the weights and repeats the
trial. It is necessary to begin with coarse preparatory tests, to
accustom the operatee to the character of the work. After a minute
or two the operator may begin to record results, and the testing may
go for several minutes, until the hand begins to tire, the judgment
to be confused, and blunders to arise. Practice does not seem to
increase the delicacy of perception after the first few trials, so
much as might be expected.
D.--WHISTLES FOR TESTING THE UPPER LIMITS OF AUDIBLE SOUND IN
DIFFERENT INDIVIDUALS.
The base of the inner tube of the whistle is the foremost end of a
plug, that admits of being advanced or withdrawn by screwing it out
or in; thus the depth of the inner tube of the whistle can be varied
at pleasure. The more nearly the plug is screwed home, the less is
the depth of the whistle and the more shrill does its note become,
until a point is reached at which, although the air that proceeds
from it vibrates as violently as before, as shown by its effect on a
sensitive flame, the note ceases to be audible.
The number of vibrations per second in the note of a whistle or
other "closed pipe" depends on its depth. The theory of acoustics
shows that the length of each complete vibration is four times that
of the depth of the closed pipe, and since experience proves that
all sound, whatever may be its pitch, is propagated at the same rate,
which under ordinary conditions of temperature and barometric
pressure may be taken at 1120 feet, or 13,440 inches per second,--it
follows that the number of vibrations in the note of a whistle may
be found by dividing 13,440 by four times the depth, measured in
inches, of the inner tube of the whistle. This rule, however,
supposes the vibrations of the air in the tube to be strictly
longitudinal, and ceases to apply when the depth of the tube is less
than about one and a half times its diameter. When the tube is
reduced to a shallow pan, a note may still be produced by it, but
that note has reference rather to the diameter of the whistle than
to its depth, being sometimes apparently unaltered by a further
decrease of depth. The necessity of preserving a fair proportion
between the diameter and the depth of a whistle is the reason why
these instruments, having necessarily little depth, require to be
made with very small bores.
The depth of the inner tube of the whistle at any moment is shown by
the graduations on the outside of the instrument. The lower portion
of the instrument as formerly made for me by the late Mr. Tisley,
optician, Brompton Road,[28] is a cap that surrounds the body of the
whistle, and is itself fixed to the screw that forms the plug. One
complete turn of the cap increases or diminishes the depth of the whistle,
by an amount equal to the interval between two adjacent threads of the
screw. For mechanical convenience, a screw is used whose pitch is 25 to
the inch; therefore one turn of the cap moves the plug one twenty-fifth
of an inch, or ten two-hundred-and-fiftieths. The edge of the cap is
divided into ten parts, each of which corresponds to the tenth of a
complete turn; and, therefore, to one two-hundred-and-fiftieth of an
inch. Hence in reading off the graduations the tens are shown on the
body of the whistle, and the units are shown on the edge of the cap.
The scale of the instrument having for its unit the two-hundred-and-
fiftieth part of an inch, it follows that the number of vibrations
in the note of the whistle is to be found by dividing (13440 x 250)/4
or 84,000, by the graduations read off on its scale.
A short table is annexed, giving the number of vibrations calculated
by this formula, for different depths, bearing in mind that the
earlier entries cannot be relied upon unless the whistle has a very
minute bore, and consequently a very feeble note.
===================================
| Scale Readings | Corresponding |
| (one division | Number of |
| = 1/250 | Vibrations |
| of an inch). | per Second |
|----------------+----------------|
| 10 | 84,000 |
| 15 | 56,000 |
| 20 | 42,000 |
| 25 | 33,600 |
| 30 | 28,000 |
| 35 | 24,000 |
| 40 | 21,000 |
| 45 | 28,666 |
| 50 | 16,800 |
| 55 | 15,273 |
| 60 | 14,000 |
| 65 | 12,923 |
| 70 | 12,000 |
| 75 | 11,200 |
| 80 | 10,500 |
| 85 | 9,882 |
| 90 | 9,333 |
| 95 | 8,842 |
| 100 | 8,400 |
| 105 | 8,000 |
| 110 | 7,591 |
| 115 | 7,305 |
| 120 | 7,000 |
| 125 | 6,720 |
| 130 | 6,461 |
===================================
[Footnote 28: Mr. Hawksley, surgical instrument maker 307 Oxford
Street also makes these.]
The largest whistles suitable for experiments on the human ear, have
an inner tube of about 0.16 inches in diameter, which is equal to 40
units of the scale. Consequently in these instruments the theory of
closed pipes ceases to be trustworthy when the depth of the whistle
is less than about 60 units. In short, we cannot be sure of sounding
with them a higher note than one of 14,000 vibrations to the second,
unless we use tubes of still smaller bore. In some of my experiments
I was driven to use very fine tubes indeed, not wider than those
little glass tubes that hold the smallest leads for Mordan's pencils.
I have tried without much success to produce a note that should be
both shrill and powerful, and correspond to a battery of small
whistles, by flattening a piece of brass tube, and passing another
sheet of brass up it, and thus forming a whistle the whole width of
the sheet, but of very small diameter from front to back. It made a
powerful note, but not a very pure one. I also constructed an
annular whistle by means of three cylinders, one sliding within the
other two, and graduated as before.
When the limits of audibility are approached, the sound becomes much
fainter, and when that limit is reached, the sound usually gives
place to a peculiar sensation, which is not sound but more like
dizziness, and which some persons experience to a high degree. Young
people hear shriller sounds than older people, and I am told there
is a proverb in Dorsetshire, that no agricultural labourer who is
more than forty years old, can hear a bat squeak. The power of
hearing shrill notes has nothing to do with sharpness of hearing,
any more than a wide range of the key-board of a piano has to do
with the sound of the individual strings. We all have our limits,
and that limit may be quickly found by these whistles in every case.
The facility of hearing shrill sounds depends in some degree on the
position of the whistle, for it is highest when it is held exactly
opposite the opening of the ear. Any roughness of the lining of the
auditory canal appears to have a marked effect in checking the
transmission of rapid vibrations when they strike the ear obliquely.
I myself feel this in a marked degree, and I have long noted the
fact in respect to the buzz of a mosquito. I do not hear the
mosquito much as it flies about, but when it passes close by my ear
I hear a "ping," the suddenness of which is very striking. Mr. Dalby,
the aurist, to whom I gave one of these instruments, tells me he
uses it for diagnoses. When the power of hearing high notes is
wholly lost, the loss is commonly owing to failure in the nerves,
but when very deaf people are still able to hear high notes if they
are sounded with force, the nerves are usually all right, and the
fault lies in the lining of the auditory canal.
E.--QUESTIONS ON VISUALISING AND OTHER ALLIED FACULTIES.
The Questions that I circulated were as follows; there was an
earlier and uncomplete form, which I need not reproduce here.
The object of these Questions is to elicit the degree in which
different persons possess the power of seeing images in their mind's
eye, and of reviving past sensations.
From inquiries I have already made, it appears that remarkable
variations exist both in the strength and in the quality of these
faculties, and it is highly probable that a statistical inquiry into
them will throw light upon more than one psychological problem.
Before addressing yourself to any of the Questions on the opposite
page, think of some definite object--suppose it is your
breakfast-table as you sat down to it this morning--and consider
carefully the picture that rises before your mind's eye.
1. _Illumination_.--Is the image dim or fairly clear? Is its
brightness comparable to that of the actual scene?
2. _Definition_.--Are all the objects pretty well defined at the
same time, or is the place of sharpest definition at any one moment
more contracted than it is in a real scene?
3. _Colouring_.--Are the colours of the china, of the toast, bread
crust, mustard, meat, parsley, or whatever may have been on the table,
quite distinct and natural?
4. _Extent of field of view_.--Call up the image of some panoramic
view (the walls of your room might suffice), can you force yourself
to see mentally a wider range of it than could be taken in by any
single glance of the eyes? Can you mentally see more than three
faces of a die, or more than one hemisphere of a globe at the same
instant of time?
5. _Distance of images_.--Where do mental images appear to be
situated? within the head, within the eye-ball, just in front of the
eyes, or at a distance corresponding to reality? Can you project
an image upon a piece of paper?
6. _Command over images_.--Can you retain a mental picture steadily
before the eyes? When you do so, does it grow brighter or dimmer?
When the act of retaining it becomes wearisome, in what part of the
head or eye-ball is the fatigue felt?
7. _Persons_.--Can you recall with distinctness the features of all
near relations and many other persons? Can you at will cause your
mental image of any or most of them to sit, stand, or turn slowly
round? Can you deliberately seat the image of a well-known person
in a chair and see it with enough distinctness to enable you to
sketch it leisurely (supposing yourself able to draw)?
8. _Scenery_.--Do you preserve the recollection of scenery with much
precision of detail, and do you find pleasure in dwelling on it? Can
you easily form mental pictures from the descriptions of scenery
that are so frequently met with in novels and books of travel?
9. _Comparison with reality_.--What difference do you perceive
between a very vivid mental picture called up in the dark, and a
real scene? Have you ever mistaken a mental image for a reality when
in health and wide awake?
10. _Numerals and dates_.--Are these invariably associated in your
mind with any peculiar mental imagery, whether of written or printed
figures, diagrams, or colours? If so, explain fully, and say if you
can account for the association?
11.--_Specialities_.--If you happen to have special aptitudes for
mechanics, mathematics (either geometry of three dimensions or pure
analysis), mental arithmetic, or chess-playing blindfold, please
explain fully how far your processes depend on the use of visual
images, and how far otherwise?
12. Call up before your imagination the objects specified in the six
following paragraphs, numbered A to F, and consider carefully
whether your mental representation of them generally, is in each
group very faint, faint, fair, good, or vivid and comparable to the
actual sensation:--
A. _Light and colour_.--An evenly clouded sky (omitting all landscape),
first bright, then gloomy. A thick surrounding haze, first white,
then successively blue, yellow, green, and red.
B. _Sound_.--The beat of rain against the window panes, the crack of
a whip, a church bell, the hum of bees, the whistle of a railway,
the clinking of tea-spoons and saucers, the slam of a door.
C. _Smells_.--Tar, roses, an oil-lamp blown out, hay, violets, a fur
coat, gas, tobacco.
D. _Tastes_.--Salt, sugar, lemon juice, raisins, chocolate,
currant jelly.
E. _Touch_.--Velvet, silk, soap, gum, sand, dough, a crisp dead leaf,
the prick of a pin.
F. _Other sensations_.--Heat, hunger, cold, thirst, fatigue, fever,
drowsiness, a bad cold.
13. _Music_.--Have you any aptitude for mentally recalling music, or
for imagining it?
14. _At different ages_.--Do you recollect what your powers of
visualising, etc., were in childhood? Have they varied much within
your recollection?
_General remarks_.--Supplementary information written here, or on
a separate piece of paper, will be acceptable.
INDEX
_For an analysis of the several chapters, see Table of Contents._
Abbadie, A. d'
Aborigines
About, E.
Abstract ideas,
like composite portraits;
are formed with difficulty
Admiralty, records of lives of sailors
Adoption
Africa,
oxen;
captive animals;
races of men
_Alert_, H.M.S.,
the crew of
Alexander the Great,
medals of;
his help to Aristotle
America,
captive animals;
change of population
Animals and birds,
their attachments and aversions
ANTECHAMBER OF CONSCIOUSNESS
ANTHROPOMETRIC REGISTERS;
anthropometric committee;
laboratories
Appold, Mr.
Arabs,
their migrations
Ashurakbal,
his menagerie
ASSOCIATIONS
(_see also_ Psychometric experiments)
Assyria,
captive animals
Athletic feats in present and past generations
Augive, or ogive
Austin, A.L.
Australia,
tame kites;
change of population
Automatic thought
Aversion
Barclay, Capt.,
of Uri
Barrel
Barth, Dr.
Bates, W.H.
Baume, Dr.
Belief (_ie_ Faith)
Bevington, Miss L.
Bible, family
Bidder, G.
Blackburne, Mr.
Blake, the artist
Bleuler and Lehman
Blind, the
Blood, terror at
BODILY QUALITIES
Boisbaudran, Lecoq de
Breaking out (violent passion)
Brierre de Boismont
Bruhl, Prof.
Burton, Capt.
Bushmen,
their skill in drawing;
in Damara Land
Campbell, J. (of Islay)
Candidates, selection of
Captive Animals (_see_ Domestication of Animals)
Cats can hear very shrill notes
Cattle,
their terror at blood;
gregariousness of;
renders them easy to tend;
cow guarding her newly-born calf;
cattle highly prized by Damaras
Celibacy as a religious exercise;
effect of endowments upon;
prudential;
to prevent continuance of an inferior race
Centesimal grades
Chance, influence of, in test experiments
Change, love of, characteristic of civilised man
CHARACTER;
observations on at schools;
changing phases of
Charterhouse College
Cheltenham College
Chess, played blindfold
Children,
mental imagery;
associations;
effect of illness on growth of head;
moral impressions on;
they and their parents understand each other;
can hear shrill notes
Chinese, the
Clock face, origin of some Number-Forms
Colleges, celibacy of Fellows of
COLOUR ASSOCIATIONS
(_see_ also chap. on Visionaries);
colour blindness
Comfort, love of, a condition of domesticability
Competitive examinations
COMPOSITE PORTRAITURE;
also Memoirs I., II., and III. in Appendix
Composite origin of some visions;
of ideas;
of memories
Composition,
automatic;
literary
CONCLUSION
Conscience,
defective in criminals;
its origin
Consciousness
(_see_ Antechamber of);
ignorance of its relation to the unconscious lives of cells of organism;
its limited ken
Consumption, types of features connected with
Cooper, Miss
CRIMINALS AND THE INSANE;
criminals, their features;
their peculiarities of character;
their children
Cromwell's soldiers
Cuckoo
DALTON,
colour blindness
was a Quaker
Damaras,
their grade of sensitivity;
their wild cattle and gregariousness;
their pride in them;
races of men in Damara Land
Dante
Darwin, Charles,
impulse given by him to new lines of thought;
on conscience;
notes on twins;
letter of Mr. A. L. Austin forwarded by
Darwin, Lieut., R.E.,
photographs of Royal Engineers
Deaf-mutes
Death, fear of; its orderly occurrence;
death and reproduction of
cells, and their unknown relation to
consciousness
Despine, Prosper
Difference, verbal difficulty in defining
many grades of
Discipline, ascetic
_Discovery_, H.M.S., the crew of
Discrimination of weights by handling
them, etc.
Dividualism; also
Doctrines, diversity of
Dogs, their capacity for hearing shrill
notes
DOMESTICATION OF ANIMALS
Dreaming
Du Cane, Sir E.
Duncan, Dr. Mathews
EARLSWOOD ASYLUM for idiots
EARLY AND LATE MARRIAGES
EARLY SENTIMENTS
Ecstasy
Editors of newspapers
Egg, raw and boiled, when spun
Egypt, captive animals
Ellis, Rev. Mr. (Polynesia)
Emigrants, value of their breed;
migration of barbarian races
ENDOWMENTS
ENERGY
Engineers, Royal, features of
English race, change of type; colour
of hair; one direction in which
it might be improved; change
of stature; various components of
ENTHUSIASM
Epileptic constitution
Eskimo, faculty of drawing and map-making
Eugenic, definition of the word
Events, observed order of