delicacy with which weights may be discriminated by handling them. I
do so because the principle on which it is based may be adopted in
apparatus for testing other senses, and its description and the
conditions of its use will illustrate the desiderata and
difficulties of all such investigations.
A series of test weights is a simple enough idea--the difficulty
lies in determining the particular sequence of weights that should
be employed. Mine form a geometric series, for the reason that when
stimuli of all kinds increase by geometric grades the sensations
they give rise to will increase by arithmetic grades, so long as the
stimulus is neither so weak as to be barely felt, nor so strong as
to excite fatigue. My apparatus, which is explained more fully in the
Appendix, consists of a number of common gun cartridge cases filled
with alternate layers of shot, wool, and wadding, and then closed in
the usual way. They are all identical in appearance, and may be said
to differ only in their specific gravities. They are marked in
numerical sequence with the register numbers, 1, 2, 3, etc., but
their weights are proportioned to the numbers of which 1, 2, 3, etc.,
are the logarithms, and consequently run in a geometric series.
Hence the numbers of the weights form a scale of equal degrees of
sensitivity. If a person can just distinguish between the weights
numbered 1 and 3, he can also just distinguish between 2 and 4, 3 and
5, and any other pair of weights of which the register number of
the one exceeds that of the other by 2. Again, his coarseness of
discrimination is exactly double of that of another person who can
just distinguish pairs of weights differing only by 1, such as 1 and
2, 2 and 3, 3 and 4, and so on. The testing is performed by handing
pairs of weights to the operatee until his power of discrimination
is approximately made out, and then to proceed more carefully. It is
best now, for reasons stated in the Appendix, to hand to the
operatee sequences of three weights at a time, after shuffling them.
These he has to arrange in their proper order, with his eyes shut,
and by the sense of their weight alone. The operator finally records
the scale interval that the operatee can just appreciate, as being
the true measure of the coarseness (or the inverse measure of the
delicacy) of the sensitivity of the operatee.
It is somewhat tedious to test many persons in succession, but any
one can test his own powers at odd and end times with ease and nicety,
if he happens to have ready access to suitable apparatus.
The use of tests, which, objectively speaking, run in a geometric
series, and subjectively in an arithmetic one, may be applied to
touch, by the use of wire-work of various degrees of fineness; to
taste, by stock bottles of solutions of salt, etc., of various
strengths; to smell, by bottles of attar of rose, etc., in various
degrees of dilution.
The tests show the sensitivity at the time they are made, and give
an approximate measure of the discrimination with which the operatee
habitually employs his senses. It does not measure his capacity for
discrimination, because the discriminative faculty admits of much
education, and the test results always show increased delicacy after
a little practice. However, the requirements of everyday life
educate all our faculties in some degree, and I have not found the
performances with test weights to improve much after a little
familiarity with their use. The weights have, as it were, to be
played with at first, then they must be tried carefully on three or
four separate occasions.
I did not at first find it at all an easy matter to make test
weights so alike as to differ in no other appreciable respect than
in their specific gravity, and if they differ and become known apart,
the knowledge so acquired will vitiate future judgments in various
indirect ways. Similarity in outward shape and touch was ensured by
the use of mechanically-made cartridge cases; dissimilarity through
any external stain was rendered of no hindrance to the experiment by
making the operatee handle them in a bag or with his eyes shut. Two
bodies may, however, be alike in weight and outward appearance and
yet behave differently when otherwise mechanically tested, and,
consequently, when they are handled. For example, take two eggs, one
raw and the other hard boiled, and spin them on the table; press the
finger for a moment upon either of them whilst it is still spinning:
if it be the hard-boiled egg it will stop as dead as a stone: if it
be the raw egg, after a little apparent hesitation, it will begin
again to rotate. The motion of its shell had alone been stopped; the
internal part was still rotating and this compelled the shell to
follow it. Owing to this cause, when we handle the two eggs, the one
feels "quick" and the other does not. Similarly with the cartridges,
when one is rather more loosely packed than the others the
difference is perceived on handling them. Or it may have one end
heavier than the other, or else its weight may not be equally
distributed round its axis, causing it to rest on the table with the
same part always lowermost; differences due to these causes are also
easily perceived when handling the cartridges. Again, one of two
similar cartridges may balance perfectly in all directions, but the
weight of one of them may be disposed too much towards the ends, as
in a dumb-bell, or gathered too much towards the centre. The period
of oscillation will differ widely in the two cases, as may be shown
by suspending the cartridges by strings round their middle so that
they shall hang horizontally, and then by a slight tap making them
spin to and fro round the string as an axis.
The touch is very keen in distinguishing all these peculiarities. I
have mentioned them, and might have added more, to show that
experiments on sensitivity have to be made in the midst of pitfalls
warily to be avoided. Our apparently simplest perceptions are very
complex. We hardly ever act on the information given by only one
element of one sense, and our sensitivity in any desired direction
cannot be rightly determined except by carefully-devised apparatus
judiciously used.
WHISTLES FOR AUDIBILITY OF SHRILL NOTES.
I contrived a small whistle for conveniently ascertaining the upper
limits of audible sound in different persons, which Dr. Wollaston
had shown to vary considerably. He used small pipes, and found much
difficulty in making them. I made a very small whistle from a brass
tube whose internal diameter was less than one-tenth of an inch in
diameter. A plug was fitted into the lower end of the tube, which
could be pulled out or pushed in as much as desired, thereby causing
the length of the bore of the whistle to be varied at will. When the
bore is long the note is low; when short, it is high. The plug was
graduated, so that the precise note produced by the whistle could be
determined by reading off the graduations and referring to a table.
(See Appendix.)
On testing different persons, I found there was a remarkable falling
off in the power of hearing high notes as age advanced. The persons
themselves were quite unconscious of their deficiency so long as
their sense of hearing low notes remained unimpaired. It is an only
too amusing experiment to test a party of persons of various ages,
including some rather elderly and self-satisfied personages. They
are indignant at being thought deficient in the power of hearing, yet
the experiment quickly shows that they are absolutely deaf to shrill
notes which the younger persons hear acutely, and they commonly
betray much dislike to the discovery. Every one has his limit, and
the limit at which sounds become too shrill to be audible to any
particular person can be rapidly determined by this little instrument.
Lord Rayleigh and others have found that sensitive flames are
powerfully affected by the vibrations of whistles that are too rapid
to be audible to ordinary ears.
I have tried experiments with all kinds of animals on their
powers of hearing shrill notes. I have gone through the whole
of the Zoological Gardens, using an apparatus arranged for the
purpose. It consists of one of my little whistles at the end of a
walking-stick--that is, in reality, a long tube; it has a bit of
india-rubber pipe under the handle, a sudden squeeze upon which
forces a little air into the whistle and causes it to sound. I hold
it as near as is safe to the ears of the animals, and when they are
quite accustomed to its presence and heedless of it, I make it sound;
then if they prick their ears it shows that they hear the whistle; if
they do not, it is probably inaudible to them. Still, it is very
possible that in some cases they hear but do not heed the sound. Of
all creatures, I have found none superior to cats in the power of
hearing shrill sounds; it is perfectly remarkable what a faculty
they have in this way. Cats, of course, have to deal in the dark
with mice, and to find them out by their squealing. Many people
cannot hear the shrill squeal of a mouse. Some time ago, singing
mice were exhibited in London, and of the people who went to hear
them, some could hear nothing, whilst others could hear a little, and
others again could hear much. Cats are differentiated by natural
selection until they have a power of hearing all the high notes made
by mice and other little creatures that they have to catch. A cat
that is at a very considerable distance, can be made to turn its ear
round by sounding a note that is too shrill to be audible by almost
any human ear. Small dogs also hear very shrill notes, but large
ones do not. I have walked through the streets of a town with an
instrument like that which I used in the Zoological Gardens, and
made nearly all the little dogs turn round, but not the large ones.
At Berne, where there appear to be more large dogs lying idly about
the streets than in any other town in Europe, I have tried the
whistle for hours together, on a great many large dogs, but could
not find one that heard it. Ponies are sometimes able to hear very
high notes. I once frightened a pony with one of these whistles in
the middle of a large field. My attempts on insect hearing have been
failures.
ANTHROPOMETRIC REGISTERS.
When shall we have anthropometric laboratories, where a man may,
when he pleases, get himself and his children weighed, measured, and
rightly photographed, and have their bodily faculties tested by the
best methods known to modern science? The records of growth of
numerous persons from childhood to age are required before it can be
possible to rightly appraise the effect of external conditions upon
development, and records of this kind are at present non-existent.
The various measurements should be accompanied by photographic
studies of the features in full face and in profile, and on the same
scale, for convenience of comparison.
We are all lazy in recording facts bearing on ourselves, but parents
are glad enough to do so in respect to their children, and they
would probably be inclined to avail themselves of a laboratory where
all that is required could be done easily and at small cost. These
domestic records would hereafter become of considerable biographical
interest. Every one of us in his mature age would be glad of a series
of pictures of himself from childhood onwards, accompanied by
physical records, and arranged consecutively with notes of current
events by their sides. Much more would he be glad of similar
collections referring to his father, mother, grandparents, and other
near relatives. It would be peculiarly grateful to the young to
possess likenesses of their parents and those whom they look upon as
heroes, taken when they were of the same age as themselves. Boys are
too apt to think of their parents as having always been elderly men,
because they have insufficient data to construct imaginary pictures
of them as they were in their youth.
The cost of taking photographs in batches is so small, and the time
occupied is so brief, when the necessary preparations have been made
and the sitters are ready at hand, that a practice of methodically
photographing schoolboys and members of other large institutions
might easily be established. I, for one, should dearly prize the
opportunity of visiting the places where I have been educated, and
of turning over pages showing myself and my companions as we were in
those days. But no such records exist; the institutions last and
flourish, the individuals who pass through them are dispersed and
leave few or no memorials behind. It seems a cruel waste of
opportunity not to make and keep these brief personal records in a
methodical manner. The fading of ordinary photographic prints is no
real objection to keeping a register, because they can now be
reproduced at small charge in permanent printers' ink, by the
autotype and other processes.
I have seen with admiration, and have had an opportunity of availing
myself of, the newly-established library of well-ordered folios at
the Admiralty, each containing a thousand pages, and each page
containing a brief summary of references to the life of a particular
seaman. There are already 80,000 pages, and owing to the excellent
organisation of the office it is a matter of perfect ease to follow
out any one of these references, and to learn every detail of the
service of any seaman. A brief register of measurements and events in
the histories of a large number of persons, previous to their
entering any institution and during their residence in it, need not
therefore be a difficult matter to those who may take it in hand
seriously and methodically.
The recommendation I would venture to make to my readers is to
obtain photographs and ordinary measurements periodically of
themselves and their children, making it a family custom to do so,
because, unless driven by some custom, the act will be postponed
until the opportunity is lost. Let those periodical photographs be
full and side views of the face on an adequate scale, adding any
others that may be wished, but not omitting these. As the portraits
accumulate have collections of them autotyped. Keep the prints
methodically in a family register, writing by their side careful
chronicles of illness and all such events as used to find a place on
the fly-leaf of the Bible of former generations, and inserting other
interesting personal facts and whatever anthropometric data can be
collected.
Those who care to initiate and carry on a family chronicle
illustrated by abundant photographic portraiture, will produce a
work that they and their children and their descendants in more
remote generations will assuredly be grateful for. The family tie
has a real as well as a traditional significance. The world is
beginning to awaken to the fact that the life of the individual is
in some real sense a prolongation of those of his ancestry. His
vigour, his character, and his diseases are principally derived from
theirs; sometimes his faculties are blends of ancestral qualities;
but more frequently they are mosaics, patches of resemblance to one
or other of them showing now here and now there. The life-histories
of our relatives are prophetic of our own futures; they are far more
instructive to us than those of strangers, far more fitted to
encourage and to forewarn us. If there be such a thing as a natural
birthright, I can conceive of none superior to the right of the
child to be informed, at first by proxy through his guardians, and
afterwards personally, of the life-history, medical and other, of
his ancestry. The child is thrust into existence without his having
any voice at all in the matter, and the smallest amend that those
who brought him here can make, is to furnish him with all the
guidance they can, including the complete life-histories of his near
progenitors.
The investigation of human eugenics--that is, of the conditions
under which men of a high type are produced--is at present extremely
hampered by the want of full family histories, both medical and
general, extending over three or four generations. There is no such
difficulty in investigating animal eugenics, because the generations
of horses, cattle, dogs, etc., are brief, and the breeder of any
such stock lives long enough to acquire a large amount of experience
from his own personal observation. A man, however, can rarely be
familiar with more than two or three generations of his
contemporaries before age has begun to check his powers; his working
experience must therefore be chiefly based upon records. Believing,
as I do, that human eugenics will become recognised before long as a
study of the highest practical importance, it seems to me that no
time ought to be lost in encouraging and directing a habit of
compiling personal and family histories. If the necessary materials
be brought into existence, it will require no more than zeal and
persuasiveness on the part of the future investigator to collect as
large a store of them as he may require.
UNCONSCIOUSNESS OF PECULIARITIES.
The importance of submitting our faculties to measurement lies in
the curious unconsciousness in which we are apt to live of our
personal peculiarities, and which our intimate friends often fail to
remark. I have spoken of the ignorance of elderly persons of their
deafness to high notes, but even the existence of such a peculiarity
as colour blindness was not suspected until the memoir of Dalton in
1794. That one person out of twenty-nine or thereabouts should be
unable to distinguish a red from a green, without knowing that he
had any deficiency of colour sense, and without betraying his
deficiency to his friends, seems perfectly incredible to the other
twenty-eight; yet as a matter of fact he rarely does either the one
or the other. It is hard to convince the colour-blind of their own
infirmity. I have seen curious instances of this: one was that of a
person by no means unpractised in physical research, who had been
himself tested in matching colours. He gave me his own version of
the result, to the effect that though he might perhaps have fallen a
little short of perfection as judged by over-refined tests, his
colour sense was for all practical purposes quite good. On the other
hand, the operator assured me that when he had toned the intensities
of a pure red and a pure green in a certain proportion, the person
ceased to be able to distinguish between them! Colour blindness is
often very difficult to detect, because the test hues and tints may
be discriminated by other means than by the normal colour sense.
Ordinary pigments are never pure, and the test colours may be
distinguished by those of their adventitious hues to which the
partly colour-blind man may be sensitive. We do not suspect
ourselves to be yellow-blind by candle light, because we enjoy
pictures in the evening nearly or perhaps quite as much as in the day
time; yet we may observe that a yellow primrose laid on the white
table-cloth wholly loses its colour by candle light, and becomes as
white as a snowdrop.
In the inquiries I made on the hereditary transmission of capacity,
I was often amused by the naïve remark of men who had easily
distanced their competitors, that they ascribed their success to
their own exertions. They little recognised how much they owed to
their natural gifts of exceptional capacity and energy on the one
hand, and of exceptional love for their special work on the other.
In future chapters I shall give accounts of persons who have unusual
mental characteristics as regards imagery, visualised numerals,
colours connected with sounds and special associations of ideas,
being unconscious of their peculiarities; but I cannot anticipate
these subjects here, as they all require explanation. It will be
seen in the end how greatly metaphysicians and psychologists may err,
who assume their own mental operations, instincts, and axioms to be
identical with those of the rest of mankind, instead of being
special to themselves. The differences between men are profound, and
we can only be saved from living in blind unconsciousness of our own
mental peculiarities by the habit of informing ourselves as well as
we can of those of others. Examples of the success with which this
can be done will be found farther on in the book.
I may take this opportunity of remarking on the well-known
hereditary character of colour blindness in connection with the fact,
that it is nearly twice as prevalent among the Quakers as among the
rest of the community, the proportions being as 5.9 to 3.5 per cent.
[1] We might have expected an even larger ratio. Nearly every Quaker
is descended on both sides solely from members of a group of men and
women who segregated themselves from the rest of the world five or
six generations ago; one of their strongest opinions being that the
fine arts were worldly snares, and their most conspicuous practice
being to dress in drabs. A born artist could never have consented to
separate himself from his fellows on such grounds; he would have
felt the profession of those opinions [5] and their accompanying
practices to be a treason to his aesthetic nature. Consequently few
of the original stock of Quakers are likely to have had the
temperament that is associated with a love for colour, and it is in
consequence most reasonable to believe that a larger proportion of
colour-blind men would have been found among them than among the
rest of the population.
[Footnote 5: _Trans. Ophthalmological Soc_., 1881, p. 198.]
Again, Quakerism is a decreasing sect, weakened by yearly desertions
and losses, especially as the act of marriage with a person who is
not a member of the Society is necessarily followed by exclusion
from it. It is most probable that a large proportion of the
deserters would be those who, through reversion to some bygone
ancestor, had sufficient artistic taste to make a continuance of
Quaker practices too irksome to be endured. Hence the existing
members of the Society of Friends are a race who probably contained
in the first instance an unduly large proportion of colour-blind men,
and from whose descendants many of those who were not born colour
blind have year by year been drafted away. Both causes must have
combined with the already well-known tendency of colour blindness to
hereditary transmission, to cause it to become a characteristic of
their race. Dalton, who first discovered its existence, as a
personal peculiarity of his own, was a Quaker to his death; Young,
the discoverer of the undulatory theory of light, and who wrote
specially on colours, was a Quaker by birth, but he married outside
the body and so ceased to belong to it.
STATISTICAL METHODS.
The object of statistical science is to discover methods of
condensing information concerning large groups of allied facts into
brief and compendious expressions suitable for discussion. The
possibility of doing this is based on the constancy and continuity
with which objects of the same species are found to vary. That is to
say, we always find, after sorting any large number of such objects
in the order (let us suppose) of their lengths, beginning with the
shortest and ending with the tallest, and setting them side by side
like a long row of park palings between the same limits, their upper
outline will be identical. Moreover, it will run smoothly and not in
irregular steps. The theoretical interpretation of the smoothness of
outline is that the individual differences in the objects are caused
by different combinations of a large number of minute influences; and
as the difference between any two adjacent objects in a long row
must depend on the absence in one of them of some single influence,
or of only a few such, that were present in the other, the amount of
difference will be insensible. Whenever we find on trial that the
outline of the row is not a flowing curve, the presumption is that
the objects are not all of the same species, but that part are
affected by some large influence from which the others are free;
consequently there is a confusion of curves. This presumption is
never found to be belied.