“I suppose,” my wife suggested, “you are still a good deal interested in fingerprints?”
“Yes,” he replied, “almost necessarily, since they so constantly crop up in evidence. But apart from, that, they are curious and interesting things in a number of ways.”
“Yes,” she agreed, “interesting and curious and rather horrible—at least that is how they appear to me. I never hear of a fingerprint but my thoughts go back to that awful trial, with Reuben in the dock and poor Aunt Arabella in the witness-box giving evidence about the Thumbograph. What a dreadful time it was!”
I am afraid I was disposed to grin at the recollection, for poor Mrs. Hornby had brought the proceedings as near to farce as is humanly possible in a criminal trial where an honourable gentleman stands indicted for a felony. But I controlled my features, and, as to Thorndyke, he was, as usual, gravely sympathetic.
“Yes,” he agreed, “it was an anxious time. I was not at all confident as to how my evidence would be received by the judge and the jury; and, if they had failed to be properly impressed, Reuben would certainly have gone to penal servitude. By the way, we sent the Thumbograph back to Mrs. Hornby after the trial. Do you happen to know what she did with it?
“She didn’t do anything with it,” Juliet replied, “because I annexed it.”
“What for?” I asked, rather foolishly, perhaps.
“Can’t you imagine?” she demanded, flushing slightly. “It was a little sentimental of me, I suppose, but I kept it as a souvenir. And why not? It had been a terrible experience, but it was over, and it had ended happily, for me, at any rate. I have something to thank the Thumbograph for.”
“It is very nice of you to say that, Juliet,” said I. “But why have you never shown it to me? I have at least as much to be thankful for, though, to tell the truth, I had overlooked the fact that it was the Thumbograph that introduced us to one another.”
“Well,” said Thorndyke, “suppose you produce this disreputable little matchmaker and let us revive our memories of those stirring times. I haven’t seen a Thumbograph for years.”
“I am not surprised,” said Juliet. “The report of your evidence at the trial was enough to kill the demand for them for ever. But I will go and fetch it.”
She went away and returned in a minute or two with the souvenir, which she handed to Thorndyke; a little oblong volume, bound in red cloth with the name “Thumbograph” stamped in gold on the cover. I looked at it with a new interest as Thorndyke turned over the leaves reminiscently while Juliet looked over his shoulder.
“Doesn’t it bring all those horrors back?” saic she, “and especially poor Mrs. Hornby’s evidence. Here is Miss Colley’s thumb-print, which Reuben was supposed to have smeared, and here is Aunt Arabella’s, and here is mine, and there is that wretch Walter’s.”
“Characteristically, the best impression in the book,” said Thorndyke. “He was a remarkably capable scoundrel. He did everything well.”
“I wonder if we shall ever see him again?” I mused. “When he slipped away from the court, he seemed to vanish into thin air.”
“Yes,” said Thorndyke; “another instance of his capability. It is not so very easy for a man who is badly wanted by the police to disappear, once and for all, as he did.”
He turned over the leaves once more until he came to the one which bore the print of Reuben Hornby’s thumb. Underneath it Reuben’s name was written in pencil and, below this, the signatures of the two witnesses, “Arabella Hornby” and “Juliet Gibson.”
“Do you remember,” said Juliet, “the night Aunt Arabella and I brought the Thumbograph to your chambers? It was a thrilling experience to me.”
“And to Thorndyke too, I imagine,” said I. “For it was then that he knew for certain that the Red Thumb Mark was a forgery. I saw him make the discovery, though I did not know at the time what the discovery was. Wasn’t it so, Thorndyke?”
“It was,” he replied. “And what was even more important, I thought I had found the means of convincing the court. You are quite right, Juliet; it was a memorable occasion for me.”
As he continued to turn over the leaves and scrutinize the various thumb-prints, I reverted to our previous conversation.
“I don’t quite understand what you were doing at the Yard today,” said I. “The classification of fingerprints is interesting enough in its way. But it doesn’t specially concern us.”
“It doesn’t concern us at all,” he agreed. “But identification does. And that is where Battley’s method is valuable to us. The beauty of it is that, apart from classification for index purposes, it affords a means of rapid identification, and moreover makes it possible to express the distinctive characters of a given fingerprint in a formula. Now this is an immense convenience. We often have occasion to identify a fingerprint with an original or a photograph in our possession. But we can’t always carry the print or photograph about with us. But if we can express the characters of the print in a formula, we can enter that formula in our notebooks, and have it ready for reference at any moment.”
“But,” I objected, “a formula would hardly be sufficiently definite for a reliable identification.”
“Not, perhaps, for a final identification to swear to in evidence,” he replied, “though you would be surprised at the accuracy that is possible. But that is not the purpose aimed at. The use of the method at the Bureau is principally to enable the searchers to find a given fingerprint quickly among the thousands in the collections of single fingerprints. Our use of it will be to form an opinion rapidly on the identity of a print in which we happen to be interested. Remember, we don’t have to give evidence. Finger-print evidence, proper, is exclusively the province of the regular experts. We have only to form an opinion for our own guidance. Come,” he continued, “I have the apparatus in my bag, which is in the hall, and here is the Thumbograph with a selection of prints to operate on. Why shouldn’t we have a demonstration of the method? You will find it quite amusing.”
“It does sound rather thrilling,” said Juliet; and, thus encouraged by the vote of the predominant partner, Thorndyke went out to find his bag.
“Let me first explain the general principle of the method,” said he, when he returned with a small leather bag in his hand. “Like all really efficient methods, it is essentially simple though extremely ingenious. This is the sole apparatus that is necessary.”
As he spoke, he opened the bag and took out a magnifying glass, which was mounted on three legs, the feet of which were fixed into a brass ring which enclosed a plate of glass.
“This circular glass plate,” he explained, “is the essential part of the instrument. If you look through the lens, you will see that the glass plate has engraved on it and coloured red a central dot surrounded by seven concentric circles. The first circle is three millimetres from the dot; the other circles are each two millimetres from the next. The central space is denoted by the letter A. The spaces between the other circles are denoted, successively, by the letters B, C, D, E, F, and G; and the space outside the outermost circle is denoted by H. The letters are, of course, not marked on the glass; but I have here a diagram which shows their position.”
He laid on the table a card on which were described the seven circles, each marked with its appropriate letter, and then, taking up the Thumbograph, once more turned over the leaves.
“I think,” said he, “we will select the estimable Walter’s thumb-print as the corpus vile for our experiment. It is the best print in the book, and it has the further advantage of being a peculiarly distinctive type with a rather striking pattern. It has the general character of a whorl with a tendency towards that of a twinned loop—that is, a pair of loops folded into each other with the convexities turned in opposite directions. But we will call it a whorl, and treat it as such, merely noting the alternative character. You will see that the pattern is formed by a number of black lines, which are the impressions of the ridges on the thumb. In this print the centre of t
he patterns, or ‘core,’ consists of a pair of little loops, from which the lines meander away in a rather irregular spiral. At a little distance from the core, these lines meet another set of lines at an angle, forming a Y-shaped figure known as a ‘delta.’ There will be another delta on the opposite side of the thumb, but it is too far round to appear in this print. It would be visible in a ‘rolled impression’—that is, a print made by rolling the inked thumb over on a card or paper; but in this print, made by a single contact, only the right delta appears.
“And now as to the use of the instrument. We lay the glass plate on the print, so that the dot just touches the top of the upper loop. And now you see the masterly simplicity of the method. For, since a circle has no right or wrong way up, when once you have set the dot in the appointed place, all the other lines must be correctly placed. Without any further adjustment, they show with absolute accuracy the distance from the centre of any part of the pattern. And this distance can be expressed, quite unmistakably, by a single letter.”
He placed the instrument on the thumb-print in the book, and, having carefully adjusted it, drew out his notebook and looked at my wife.
“Now, Juliet,” said he, “just look through the lens and tell me the letter that indicates the position of the delta—which is actually the right delta, though it is the only one visible.”
Juliet peered through the magnifying glass and studied the print for a while. At length, she looked up a little doubtfully and announced:
“It seems to me that the third line cuts right through it. So it lies half in the space C and half in D. Which of the two would you call it?”
“The rule,” he replied, “is that if a character is cut by a line, it is reckoned as lying in the space outside that line.”
“Then this delta lies in the space D,” she concluded.
“Quite right,” said he. “We will mark it D; and, as the other delta is not in the print, we must mark it simply with a query. And now we proceed to the rest of the examination, the ridge-tracing and ridge-counting. We will take the tracing first. What you would have to do if both the deltas were visible would be to follow the ridge that runs from the left delta towards the right. Obviously, it must take one of three courses: it may pass below, or outside, the right delta, or below, or inside, or it may meet, or nearly meet, the corresponding ridge from the right delta. Those are the three categories: outside, inside, or meeting, by the initials, I, M, O.”
“But,” objected Juliet, “as the left delta is not visible, it is impossible to trace a ridge from it.”
“That might be true in some cases,” replied Thorndyke, “but it is not in this, for, if you look at the print, you will see that, wherever the left delta may have been, a ridge passing from it towards the right must have passed well outside the right delta.”
Juliet examined the print again and agreed that it was so.
“Very well,” said Thorndyke, “then we will mark it O, and proceed to the ridge-counting, which will complete the formula. You have to count the ridges between the centre of the core and the delta. Put aside the measuring glass and use my lens instead; and I will give you a point to help you to count the ridges.”
He handed her his pocket lens, and produced from his bag what looked suspiciously like a dentist’s excavator, with the sharp point of which he indicated the ridges that were to be counted. Then he laid a visiting-card on the print to give a straight line from the centre to the delta, and she proceeded to count along its edge with the point of the excavator. Having gone over the ground twice, she announced the result.
“I make it twelve. But I am not quite sure, as some of the ridges fork, and might be counted as one or two. Will you count them?”
Thorndyke took the excavator from her and rapidly checked her result.
“Yes,” said he, “I agree with you. I think we may safely put it down as twelve, though the bifurcations do, as you say, create a slight ambiguity. If the other delta had been visible there would, of course, have been a second circle-reading and a second ridge-count, which would obviously have been an advantage for identification. Still, what we have done gives us the main distinctive characters of this print, and we can express them by a simple formula of a few letters and numbers. Thus, the type of pattern is a whorl, with something of the character of a twinned loop. Accordingly, we put down a W with T.L. in brackets. The core, or central character—the pair of little, loops—lies entirely in the circle A. Now, there are five kinds of ‘A’ cores: the plain eye—just a tiny circle—the eye enclosing some smaller character, the left-hand spiral, the right-hand spiral, and any other ‘A’ form of an unclassifiable type. Now, in this print, the core is a left-hand, or anti-clockwise spiral, and accordingly belongs to the category A3. The delta, we agreed, lies in the space D. The ridge-tracing was outside—O—and the ridge-count twelve. We can express all these facts in a formula, thus:
“Walter Hornby. Right thumb.
W (? T.L.), A3, ?, O, D, ?, 12.”
“That is concise enough,” I remarked. “But, after all, it gives you only a skeleton of the pattern. It would not enable you to identify a print with any approach to certainty.”
“It does not aim at certainty,” he replied, “but merely at such a degree of probability as would justify action or further research. But I think you hardly appreciate the degree of probability that this formula expresses. It records five different positive characters and one negative. Now, taking the five only, if we accept the very modest chance of four to one against each of these characters being present in a print which is not Walter Hornby’s, the cumulative effect of the five together yields a chance of over a thousand to one against the print being that of some person other than Walter Hornby.
“But, for our purposes, we are not obliged to stop at these five characters. We can add others; and we can locate those others either by the use of Battley’s circles or by ridge-counting with a direction-line. For instance, in this print, to the left of the core and a little downwards, the seventh ridge shows one of those little loops known as ‘lakes,’ the ninth bifurcates, and the eleventh has another, larger lake. To the right of the core the third ridge has a small lake, the fifth ridge bifurcates, the eighth has a free end, and the tenth bifurcates. There are seven additional characters which we can add to our formula, giving us twelve characters in all, the cumulative effect of which is a probability of over sixteen millions to one against the print being the thumb-print of any person other than Walter Hornby, and that is near enough to certainty for our purpose. It would undoubtedly justify an arrest; and we could leave the final proof or disproof to the experts.”
He added the extra characters to the formula in his notebook, and showed us the completed entry; which certainly afforded convincing testimony to the efficiency of the method. In fact, it impressed me—and my wife, too—so profoundly that, in an access of enthusiasm, we fell upon the Thumbograph forthwith, and with the aid of Chief Inspector Battley’s ingenious instrument, proceeded to construct formulas to express the characters of the other thumb-prints in the book, while Thorndyke smoked his pipe regarded our activities with benevolent interest, seasoned by occasional advice and criticism of the results.
“It is quite an amusing game,” Juliet remarked. “If only the inventors of the Thumbograph had known of it and printed directions in the book, it might have become a fashionable drawing-room pastime, and they would have made a fortune.”
“Perhaps it is as well that they did not,” said I. “The Thumbograph was a dangerous toy, as we discovered—or rather, as Thorndyke did.”
“Yes,” Thorndyke agreed, “it was a mischievous plaything. But don’t forget that it acted both ways. If it supplied the false accusation, it also supplied the conclusive answer. Walter Hornby had more reason than any of us to regret that he ever set eyes on the Thumbograph. And it may be that he has not yet come to the end of those reasons. He has evaded justice so far. But the debt is still outstanding.”
CHAPTER X
Mr. Woodburn’s Story
Inventors are a much-misunderstood class. The common man, in his vanity and egotism, supposes that they exist to supply him with various commodities of which he dimly perceives the need. But this is an entirely mistaken view. The inventor produces his invention because, in the existing circumstances, it has become possible. It is true that he, himself, tends to confuse the issues by persuading himself optimistically that his invention has a real and important utility. His inventive mind goes so far as to create an imaginary consumer, so that he sees life in a some what false perspective. The genius who devised a family Bible which could be opened out to form a billiard table, no doubt envisaged a pious type of player who had need of some means of combining the canon of scripture with a cannon off the red; while, to the inventor of a super magic-lantern which could throw pictures on the clouds, the night sky was no more than a suitable background on which to declare the glory of Blunt’s Milky Toffee.
But this is mere self-delusion. In reality, the inventor is concerned with his invention. Its use is but a side issue which hovers vaguely on the periphery of his mental field of vision. I emphasise the fact, because it has a bearing on the events which I am recording. For our invaluable laboratory assistant, Polton, was an inveterate inventor, and, being also an accomplished and versatile craftsman, was able to turn out his inventions in a completely realised form.
So it happened that a certain large cupboard in the laboratory was a veritable museum of the products of his inventive genius and manual skill; examples of ingenuity—sometimes fantastically misguided—the utility of which he would expound to Thorndyke and me with pathetic earnestness and appeals to “give them a trial.” There were spectacles which enabled the wearer to see behind him, there was a periscope walking-stick with which you could see round a corner, a large pedometer with movable dials for metres and yards and a micrometer adjustment of impracticable accuracy, and all sorts of clockwork devices and appliances for out-of-the-way photographic operations. But optical instruments were his special passion, whence it followed that most of his inventions took an optical turn.
The Third R. Austin Freeman Megapack Page 122
