When I arrived at Thorndyke’s
chambers on the following morning, I found my friend
already hard at work. Breakfast was laid at one
end of the table, while at the other stood a microscope
of the pattern used for examining plate-cultures of
micro-organisms, on the wide stage of which was one
of the cards bearing six thumb-prints in blood.
A condenser threw a bright spot of light on the card,
which Thorndyke had been examining when I knocked,
as I gathered from the position of the chair, which
he now pushed back against the wall.
“I see you have commenced work
on our problem,” I remarked as, in response
to a double ring of the electric bell, Polton entered
with the materials for our repast.
“Yes,” answered Thorndyke.
“I have opened the campaign, supported, as usual,
by my trusty chief-of-staff; eh! Polton?”
The little man, whose intellectual,
refined countenance and dignified bearing seemed oddly
out of character with the tea-tray that he carried,
smiled proudly, and, with a glance of affectionate
admiration at my friend, replied
“Yes, sir. We haven’t
been letting the grass grow under our feet. There’s
a beautiful negative washing upstairs and a bromide
enlargement too, which will be mounted and dried by
the time you have finished your breakfast.”
“A wonderful man that, Jervis,”
my friend observed as his assistant retired.
“Looks like a rural dean or a chancery judge,
and was obviously intended by Nature to be a professor
of physics. As an actual fact he was first a
watchmaker, then a maker of optical instruments, and
now he is mechanical factotum to a medical jurist.
He is my right-hand, is Polton; takes an idea before
you have time to utter it but you will
make his more intimate acquaintance by-and-by.”
“Where did you pick him up?” I asked.
“He was an in-patient at the
hospital when I first met him, miserably ill and broken,
a victim of poverty and undeserved misfortune.
I gave him one or two little jobs, and when I found
what class of man he was I took him permanently into
my service. He is perfectly devoted to me, and
his gratitude is as boundless as it is uncalled for.”
“What are the photographs he was referring to?”
“He is making an enlarged facsimile
of one of the thumb-prints on bromide paper and a
negative of the same size in case we want the print
“You evidently have some expectation
of being able to help poor Hornby,” said I,
“though I cannot imagine how you propose to go
to work. To me his case seems as hopeless a one
as it is possible to conceive. One doesn’t
like to condemn him, but yet his innocence seems almost
“It does certainly look like
a hopeless case,” Thorndyke agreed, “and
I see no way out of it at present. But I make
it a rule, in all cases, to proceed on the strictly
classical lines of inductive inquiry collect
facts, make hypotheses, test them and seek for verification.
And I always endeavour to keep a perfectly open mind.
“Now, in the present case, assuming,
as we must, that the robbery has actually taken place,
there are four conceivable hypotheses: (1) that
the robbery was committed by Reuben Hornby; (2) that
it was committed by Walter Hornby; (3) that it was
committed by John Hornby, or (4) that it was committed
by some other person or persons.
“The last hypothesis I propose
to disregard for the present and confine myself to
the examination of the other three.”
“You don’t think it possible
that Mr. Hornby could have stolen the diamonds out
of his own safe?” I exclaimed.
“I incline at present to no
one theory of the matter,” replied Thorndyke.
“I merely state the hypotheses. John Hornby
had access to the diamonds, therefore it is possible
that he stole them.”
“But surely he was responsible to the owners.”
“Not in the absence of gross
negligence, which the owners would have difficulty
in proving. You see, he was what is called a gratuitous
bailee, and in such a case no responsibility for loss
lies with the bailee unless there has been gross negligence.”
“But the thumb-mark, my dear
fellow!” I exclaimed. “How can you
possibly get over that?”
“I don’t know that I can,”
answered Thorndyke calmly; “but I see you are
taking the same view as the police, who persist in
regarding a finger-print as a kind of magical touchstone,
a final proof, beyond which inquiry need not go.
Now, this is an entire mistake. A finger-print
is merely a fact a very important and significant
one, I admit but still a fact, which, like
any other fact, requires to be weighed and measured
with reference to its evidential value.”
“And what do you propose to
do first?” “I shall first satisfy myself
that the suspected thumb-print is identical in character
with that of Reuben Hornby of which, however,
I have very little doubt, for the finger-print experts
may fairly be trusted in their own speciality.”
“I shall collect fresh facts,
in which I look to you for assistance, and, if we
have finished breakfast, I may as well induct you into
your new duties.”
He rose and rang the bell, and then,
fetching from the office four small, paper-covered
notebooks, laid them before me on the table.
“One of these books,”
said he, “we will devote to data concerning Reuben
Hornby. You will find out anything you can anything,
mind, no matter how trivial or apparently irrelevant in
any way connected with him and enter it in this book.”
He wrote on the cover “Reuben Hornby” and
passed the book to me. “In this second
book you will, in like manner, enter anything that
you can learn about Walter Hornby, and, in the third
book, data concerning John Hornby. As to the
fourth book, you will keep that for stray facts connected
with the case but not coming under either of the other
headings. And now let us look at the product of
He took from his assistant’s
hand a photograph ten inches long by eight broad,
done on glazed bromide paper and mounted flatly on
stiff card. It showed a greatly magnified facsimile
of one of the thumb-prints, in which all the minute
details, such as the orifices of the sweat glands
and trifling irregularities in the ridges, which, in
the original, could be seen only with the aid of a
lens, were plainly visible to the naked eye.
Moreover, the entire print was covered by a network
of fine black lines, by which it was divided into
a multitude of small squares, each square being distinguished
by a number.
“Excellent, Polton,” said
Thorndyke approvingly; “a most admirable enlargement.
You see, Jervis, we have photographed the thumb-print
in contact with a numbered micrometer divided into
square twelfths of an inch. The magnification
is eight diameters, so that the squares are here each
two-thirds of an inch in diameter. I have a number
of these micrometers of different scales, and I find
them invaluable in examining cheques, doubtful signatures
and such like. I see you have packed up the camera
and the microscope, Polton; have you put in the micrometer?”
“Yes, sir,” replied Polton,
“and the six-inch objective and the low-power
eye-piece. Everything is in the case; and I have
put ’special rapid’ plates into the dark-slides
in case the light should be bad.”
“Then we will go forth and beard
the Scotland Yard lions in their den,” said
Thorndyke, putting on his hat and gloves.
“But surely,” said I,
“you are not going to drag that great microscope
to Scotland Yard, when you only want eight diameters.
Haven’t you a dissecting microscope or some
other portable instrument?”
“We have a most delightful instrument
of the dissecting type, of Polton’s own make he
shall show it to you. But I may have need of a
more powerful instrument and here let me
give you a word of warning: whatever you may
see me do, make no comments before the officials.
We are seeking information, not giving it, you understand.”
At this moment the little brass knocker
on the inner door the outer oak being open uttered
a timid and apologetic rat-tat.
“Who the deuce can that be?”
muttered Thorndyke, replacing the microscope on the
table. He strode across to the door and opened
it somewhat brusquely, but immediately whisked his
hat off, and I then perceived a lady standing on the
“Dr. Thorndyke?” she inquired,
and as my colleague bowed, she continued, “I
ought to have written to ask for an appointment but
the matter is rather urgent it concerns
Mr. Reuben Hornby and I only learned from him this
morning that he had consulted you.”
“Pray come in,” said Thorndyke.
“Dr. Jervis and I were just setting out for
Scotland Yard on this very business. Let me present
you to my colleague, who is working up the case with
Our visitor, a tall handsome girl
of twenty or thereabouts, returned my bow and remarked
with perfect self-possession, “My name is Gibson Miss
Juliet Gibson. My business is of a very simple
character and need not detain you many minutes.”
She seated herself in the chair that
Thorndyke placed for her, and continued in a brisk
and business-like manner
“I must tell you who I am in
order to explain my visit to you. For the last
six years I have lived with Mr. and Mrs. Hornby, although
I am no relation to them. I first came to the
house as a sort of companion to Mrs. Hornby, though,
as I was only fifteen at the time, I need hardly say
that my duties were not very onerous; in fact, I think
Mrs. Hornby took me because I was an orphan without
the proper means of getting a livelihood, and she
had no children of her own.
“Three years ago I came into
a little fortune which rendered me independent; but
I had been so happy with my kind friends that I asked
to be allowed to remain with them, and there I have
been ever since in the position of an adopted daughter.
Naturally, I have seen a great deal of their nephews,
who spend a good part of their time at the house, and
I need not tell you that the horrible charge against
Reuben has fallen upon us like a thunderbolt.
Now, what I have come to say to you is this:
I do not believe that Reuben stole those diamonds.
It is entirely out of character with all my previous
experience of him. I am convinced that he is
innocent, and I am prepared to back my opinion.”
“In what way?” asked Thorndyke.
“By supplying the sinews of
war,” replied Miss Gibson. “I understand
that legal advice and assistance involves considerable
“I am afraid you are quite correctly
informed,” said Thorndyke.
“Well, Reuben’s pecuniary
resources are, I am sure, quite small, so it is necessary
for his friends to support him, and I want you to promise
me that nothing shall be left undone that might help
to prove his innocence if I make myself responsible
for any costs that he is unable to meet. I should
prefer, of course, not to appear in the matter, if
it could be avoided.”
“Your friendship is of an eminently
practical kind, Miss Gibson,” said my colleague,
with a smile. “As a matter of fact, the
costs are no affair of mine. If the occasion
arose for the exercise of your generosity you would
have to approach Mr. Reuben’s solicitor through
the medium of your guardian, Mr. Hornby, and with
the consent of the accused. But I do not suppose
the occasion will arise, although I am very glad you
called, as you may be able to give us valuable assistance
in other ways. For example, you might answer one
or two apparently impertinent questions.”
“I should not consider any question
impertinent that you considered necessary to ask,”
our visitor replied.
“Then,” said Thorndyke,
“I will venture to inquire if any special relations
exist between you and Mr. Reuben.”
“You look for the inevitable
motive in a woman,” said Miss Gibson, laughing
and flushing a little. “No, there have been
no tender passages between Reuben and me. We
are merely old and intimate friends; in fact, there
is what I may call a tendency in another direction Walter
“Do you mean that you are engaged to Mr. Walter?”
“Oh, no,” she replied;
“but he has asked me to marry him he
has asked me, in fact, more than once; and I really
believe that he has a sincere attachment to me.”
She made this latter statement with
an odd air, as though the thing asserted were curious
and rather incredible, and the tone was evidently
noticed by Thorndyke as well as me for he rejoined
“Of course he has. Why not?”
“Well, you see,” replied
Miss Gibson, “I have some six hundred a year
of my own and should not be considered a bad match
for a young man like Walter, who has neither property
nor expectations, and one naturally takes that into
account. But still, as I have said, I believe
he is quite sincere in his professions and not merely
attracted by my money.”
“I do not find your opinion
at all incredible,” said Thorndyke, with a smile,
“even if Mr. Walter were quite a mercenary young
man which, I take it, he is not.”
Miss Gibson flushed very prettily as she replied
“Oh, pray do not trouble to
pay me compliments; I assure you I am by no means
insensible of my merits. But with regard to Walter
Hornby, I should be sorry to apply the term ‘mercenary’
to him, and yet well, I have never met
a young man who showed a stronger appreciation of the
value of money. He means to succeed in life and
I have no doubt he will.”
“And do I understand that you refused him?”
“Yes. My feelings towards
him are quite friendly, but not of such a nature as
to allow me to contemplate marrying him.”
“And now, to return for a moment
to Mr. Reuben. You have known him for some years?”
“I have known him intimately
for six years,” replied Miss Gibson.
“And what sort of character do you give him?”
“Speaking from my own observation
of him,” she replied, “I can say that
I have never known him to tell an untruth or do a dishonourable
deed. As to theft, it is merely ridiculous.
His habits have always been inexpensive and frugal,
he is unambitious to a fault, and in respect to the
‘main chance’ his indifference is as conspicuous
as Walter’s keenness. He is a generous
man, too, although careful and industrious.”
“Thank you, Miss Gibson,”
said Thorndyke. “We shall apply to you for
further information as the case progresses. I
am sure that you will help us if you can, and that
you can help us if you will, with your clear head
and your admirable frankness. If you will leave
us your card, Dr. Jervis and I will keep you informed
of our prospects and ask for your assistance whenever
we need it.”
After our fair visitor had departed,
Thorndyke stood for a minute or more gazing dreamily
into the fire. Then, with a quick glance at his
watch, he resumed his hat and, catching up the microscope,
handed the camera case to me and made for the door.
“How the time goes!” he exclaimed, as
we descended the stairs; “but it hasn’t
been wasted, Jervis, hey?”
“No, I suppose not,” I answered tentatively.
“You suppose not!” he
replied. “Why here is as pretty a little
problem as you could desire what would
be called in the jargon of the novels, a psychological
problem and it is your business to work
it out, too.”
“You mean as to Miss Gibson’s
relations with these two young men?”
“Is it any concern of ours?” I asked.
“Certainly it is,” he
replied. “Everything is a concern of ours
at this preliminary stage. We are groping about
for a clue and must let nothing pass unscrutinised.”
“Well, then, to begin with,
she is not wildly infatuated with Walter Hornby, I
“No,” agreed Thorndyke,
laughing softly; “we may take it that the canny
Walter has not inspired a grand passion.”
“Then,” I resumed, “if
I were a suitor for Miss Gibson’s hand, I think
I would sooner stand in Reuben’s shoes than
“There again I am with you,” said Thorndyke.
“Well,” I continued, “our
fair visitor conveyed to me the impression that her
evident admiration of Reuben’s character was
tempered by something that she had heard from a third
party. That expression of hers, ‘speaking
from my own observation,’ seemed to imply that
her observations of him were not in entire agreement
with somebody else’s.”
“Good man!” exclaimed
Thorndyke, slapping me on the back, to the undissembled
surprise of a policeman whom we were passing; “that
is what I had hoped for in you the capacity
to perceive the essential underneath the obvious.
Yes; somebody has been saying something about our
client, and the thing that we have to find out is,
what is it that has been said and who has been saying
it. We shall have to make a pretext for another
interview with Miss Gibson.”
“By the way, why didn’t
you ask her what she meant?” I asked foolishly.
Thorndyke grinned in my face.
“Why didn’t you?” he retorted.
“No,” I rejoined, “I
suppose it is not politic to appear too discerning.
Let me carry the microscope for a time; it is making
your arm ache, I see.”
“Thanks,” said he, handing
the case to me and rubbing his fingers; “it
is rather ponderous.”
“I can’t make out what
you want with this great instrument,” I said.
“A common pocket lens would do all that you
require. Besides, a six-inch objective will not
magnify more than two or three diameters.”
“Two, with the draw-tube closed,”
replied Thorndyke, “and the low-power eye-piece
brings it up to four. Polton made them both for
me for examining cheques, bank-notes and other large
objects. But you will understand when you see
me use the instrument, and remember, you are to make
We had by this time arrived at the
entrance to Scotland Yard, and were passing up the
narrow thoroughfare, when we encountered a uniformed
official who halted and saluted my colleague.
“Ah, I thought we should see
you here before long, doctor,” said he genially.
“I heard this morning that you have this thumb-print
case in hand.”
“Yes,” replied Thorndyke;
“I am going to see what can be done for the
“Well,” said the officer
as he ushered us into the building, “you’ve
given us a good many surprises, but you’ll give
us a bigger one if you can make anything of this.
It’s a foregone conclusion, I should say.”
“My dear fellow,” said
Thorndyke, “there is no such thing. You
mean that there is a prima facie case against
“Put it that way if you like,”
replied the officer, with a sly smile, “but
I think you will find this about the hardest nut you
ever tried your teeth on and they’re
pretty strong teeth too, I’ll say that.
You had better come into Mr. Singleton’s office,”
and he conducted us along a corridor and into a large,
barely-furnished room, where we found a sedate-looking
gentleman seated at a large writing table.
said the latter, rising and holding out his hand.
“I can guess what you’ve come for.
Want to see that thumb-print, eh?”
“Quite right,” answered
Thorndyke, and then, having introduced me, he continued:
“We were partners in the last game, but we are
on opposite sides of the board this time.”
“Yes,” agreed Mr. Singleton;
“and we are going to give you check-mate.”
He unlocked a drawer and drew forth
a small portfolio, from which he extracted a piece
of paper which he laid on the table. It appeared
to be a sheet torn from a perforated memorandum block,
and bore the pencilled inscription: “Handed
in by Reuben at 7.3 p.m., 9.3.01. J. H.”
At one end was a dark, glossy blood-stain, made by
the falling of a good-sized drop, and this was smeared
slightly, apparently by a finger or thumb having been
pressed on it. Near to it were two or three smaller
smears and a remarkably distinct and clean print of
Thorndyke gazed intently at the paper
for a minute or two, scrutinising the thumb-print
and the smears in turn, but making no remark, while
Mr. Singleton watched his impassive face with expectant
“Not much difficulty in identifying
that mark,” the official at length observed.
“No,” agreed Thorndyke;
“it is an excellent impression and a very distinctive
pattern, even without the scar.”
“Yes,” rejoined Mr. Singleton;
“the scar makes it absolutely conclusive.
You have a print with you, I suppose?”
“Yes,” replied Thorndyke,
and he drew from a wide flap-pocket the enlarged photograph,
at the sight of which Mr. Singleton’s face broadened
into a smile.
“You don’t want to put
on spectacles to look at that,” he remarked;
“not that you gain anything by so much enlargement;
three diameters is ample for studying the ridge-patterns.
I see you have divided it up into numbered squares not
a bad plan; but ours or rather Galton’s,
for we borrowed the method from him is
better for this purpose.”
He drew from the portfolio a half-plate
photograph of the thumb-print which appeared magnified
to about four inches in length. The print was
marked by a number of figures written minutely with
a fine-pointed pen, each figure being placed on an
“island,” a loop, a bifurcation or some
other striking and characteristic portion of the ridge-pattern.
“This system of marking with
reference numbers,” said Mr. Singleton, “is
better than your method of squares, because the numbers
are only placed at points which are important for
comparison, whereas your squares or the intersections
of the lines fall arbitrarily on important or unimportant
points according to chance. Besides, we can’t
let you mark our original, you know, though, of course,
we can give you a photograph, which will do as well.”
“I was going to ask you to let
me take a photograph presently,” said Thorndyke.
“Certainly,” replied Mr.
Singleton, “if you would rather have one of
your own taking. I know you don’t care to
take anything on trust. And now I must get on
with my work, if you will excuse me. Inspector
Johnson will give you any assistance you may require.”
“And see that I don’t
pocket the original,” added Thorndyke, with a
smile at the inspector who had shown us in.
“Oh, I’ll see to that,”
said the latter, grinning; and, as Mr. Singleton returned
to his table, Thorndyke unlocked the microscope case
and drew forth the instrument.
“What, are you going to put
it under the microscope?” exclaimed Mr. Singleton,
looking round with a broad smile.
“Must do something for my fee,
you know,” replied Thorndyke, as he set up the
microscope and screwed on two extra objectives to the
triple nose-piece. “You observe that there
is no deception,” he added to the inspector,
as he took the paper from Mr. Singleton’s table
and placed it between two slips of glass.
“I’m watching you, sir,”
replied the officer, with a chuckle; and he did watch,
with close attention and great interest, while Thorndyke
laid the glass slips on the microscope stage and proceeded
I also watched, and was a good deal
exercised in my mind by my colleague’s proceedings.
After a preliminary glance with the six-inch glass,
he swung round the nose-piece to the half-inch objective
and slipped in a more powerful eye-piece, and with
this power he examined the blood-stains carefully,
and then moved the thumb-print into the field of vision.
After looking at this for some time with deep attention,
he drew from the case a tiny spirit lamp which was
evidently filled with an alcoholic solution of some
sodium salt, for when he lit it I recognised the characteristic
yellow sodium flame. Then he replaced one of
the objectives by a spectroscopic attachment, and having
placed the little lamp close to the microscope mirror,
adjusted the spectroscope. Evidently my friend
was fixing the position of the “D” line
(or sodium line) in the spectrum.
Having completed the adjustments,
he now examined afresh the blood-smears and the thumb-print,
both by transmitted and reflected light, and I observed
him hurriedly draw one or two diagrams in his notebook.
Then he replaced the spectroscope and lamp in the case
and brought forth the micrometer a slip
of rather thin glass about three inches by one and
a half which he laid over the thumb-print
in the place of the upper plate of glass.
Having secured it in position by the
clips, he moved it about, comparing its appearance
with that of the lines on the large photograph, which
he held in his hand. After a considerable amount
of adjustment and readjustment, he appeared to be
satisfied, for he remarked to me
“I think I have got the lines
in the same position as they are on our print, so,
with Inspector Johnson’s assistance, we will
take a photograph which we can examine at our leisure.”
He extracted the camera a
quarter-plate instrument from its case and
opened it. Then, having swung the microscope on
its stand into a horizontal position, he produced
from the camera case a slab of mahogany with three
brass feet, on which he placed the camera, and which
brought the latter to a level with the eye-piece of
The front of the camera was fitted
with a short sleeve of thin black leather, and into
this the eye-piece end of the microscope was now passed,
the sleeve being secured round the barrel of the microscope
by a stout indiarubber band, thus producing a completely
Everything was now ready for taking
the photograph. The light from the window having
been concentrated on the thumb-print by means of a
condenser, Thorndyke proceeded to focus the image on
the ground-glass screen with extreme care and then,
slipping a small leather cap over the objective, introduced
the dark slide and drew out the shutter.
“I will ask you to sit down
and remain quite still while I make the exposure,”
he said to me and the inspector. “A very
little vibration is enough to destroy the sharpness
of the image.”
We seated ourselves accordingly, and
Thorndyke then removed the cap, standing motionless,
watch in hand, while he exposed the first plate.
“We may as well take a second,
in case this should not turn out quite perfect,”
he said, as he replaced the cap and closed the shutter.
He reversed the dark slide and made
another exposure in the same way, and then, having
removed the micrometer and replaced it by a slip of
plain glass, he made two more exposures.
“There are two plates left,”
he remarked, as he drew out the second dark slide.
“I think I will take a record of the blood-stain
He accordingly made two more exposures one
of the larger blood-stain and one of the smaller smears.
“There,” said he, with
an air of satisfaction, as he proceeded to pack up
what the inspector described as his “box of tricks.”
“I think we have all the data that we can squeeze
out of Scotland Yard, and I am very much obliged to
you, Mr. Singleton, for giving so many facilities to
your natural enemy, the counsel for the defence.”
“Not our natural enemies, doctor,”
protested Mr. Singleton. “We work for a
conviction, of course, but we don’t throw obstacles
in the way of the defence. You know that perfectly
“Of course I do, my dear sir,”
replied Thorndyke, shaking the official by the hand.
“Haven’t I benefited by your help a score
of times? But I am greatly obliged all the same.
“Good-bye, doctor. I wish
you luck, though I fear you will find it ’no
go’ this time.”
“We shall see,” replied
Thorndyke, and with a friendly wave of the hand to
the inspector he caught up the two cases and led the
way out of the building.