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 and fork and looked into my face with a smile of quiet amusement.
"It has just been borne in upon me, Jervis," said he, "that you are the most companionable fellow in the world. You have the heaven-sent gift of silence."
"If silence is the test of companionability," I answered, with a grin, "I think I can pay you a similar compliment in even more emphatic terms."
He laughed cheerfully and rejoined—
"You are pleased to be sarcastic, I observe; but I maintain my position. The capacity to preserve an opportune silence is the rarest and most precious of social accomplishments. Now, most men would have plied me with questions and babbled comments on my proceedings at Scotland Yard, whereas you have allowed me to sort out, without interruption, a mass of evidence while it is still fresh and impressive, to docket each item and stow it away in the pigeonholes of my brain. By the way, I have made a ridiculous oversight."
"What is that?" I asked.
"The 'Thumbograph.' I never ascertained whether the police have it or whether it is still in the possession of Mrs. Hornby."
"Does it matter?" I inquired.
"Not much; only I must see it. And perhaps it will furnish an excellent pretext for you to call on Miss Gibson. As I am busy at the hospital this afternoon and Polton has his hands full, it would be a good plan for you to drop in at Endsley Gardens—that is the address, I think—and if you can see Miss Gibson, try to get a confidential chat with her, and extend your knowledge of the manners and customs of the three Messieurs Hornby. Put on your best bedside manner and keep your weather eye lifting. Find out everything you can as to the characters and habits of those three gentlemen, regardless of all scruples of delicacy. Everything is of importance to us, even to the names of their tailors."
"And with regard to the 'Thumbograph'?"
"Find
