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 to focus.
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 microscope.
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 light-tight connection.
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 on them."
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 well."
"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."
"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.
Confidences
During our walk home my friend was unusually thoughtful and silent, and his face bore a look of concentration under which I thought I could detect, in spite of his habitually impassive expression, a certain suppressed excitement of a not entirely unpleasurable kind. I forbore, however, from making any remarks or asking questions, not only because I saw that he was preoccupied, but also because, from my knowledge of the man, I judged that he would consider it his duty to keep his own counsel and to make no unnecessary confidences even to me.
On our arrival at his chambers he immediately handed over the camera to Polton with a few curt directions as to the development of the plates, and, lunch being already prepared, we sat down at the table without delay.
We had proceeded with our meal in silence for some time when Thorndyke suddenly laid down his knife