endeavouring to change the subject to one more promising.
"Just copying the peculiar shape of those marks on Phelps' arm. Perhaps we can improve on the finger-print method of identification. Those were the marks of human teeth."
He was glancing casually at his sketch as he displayed it to us. I wondered whether he really expected to obtain proof of the identity of at least one of the ghouls by the tooth-marks.
"It shows eight teeth, one of them decayed," he remarked. "By the way, there's no use watching here any longer. I have some more work to do in the laboratory which will keep me another day. To-morrow night I shall be ready. Andrews, in the mean time I leave the shadowing of Dana to you, and with the help of Jameson I want you to arrange to have all those connected with the case at my laboratory to-morrow night without fail."
Andrews and I had to do some clever scheming to bring pressure to bear on the various persons interested to insure their attendance, now that Craig was ready to act. Of course there was no difficulty in getting Dana Phelps. Andrews's shadows reported nothing in his actions of the following day that indicated anything. Mrs. Phelps came down to town by train and Doctor Forden motored in. Andrews even took the precaution to secure Shaughnessy and the trained nurse, Miss Tracy, who had been with Montague Phelps during his illness but had not contributed anything toward untangling the case. Andrews and myself completed the little audience.
We found Kennedy heating a large mass of some composition such as dentists use in taking impressions of the teeth.
"I shall be ready in a moment," he excused himself, still bending over his Bunsen flame. "By the way, Mr. Phelps, if you will permit me."
He had detached a wad of the softened material. Phelps, taken by surprise, allowed him to make an impression of his teeth, almost before he realised what Kennedy was doing. The precedent set, so to speak, Kennedy approached Doctor Forden. He demurred, but finally consented. Mrs. Phelps followed, then the nurse, and even Shaughnessy.
With a quick glance at each impression, Kennedy laid them aside to harden.
"I am ready to begin," he remarked at length, turning to a peculiar looking instrument, something like three telescopes pointing at a centre in which was a series of glass prisms.
"These five senses of ours are pretty dull detectives sometimes," Kennedy began. "But I find that when we are able to call in outside aid we usually find that there are no more mysteries."
He placed something in a test-tube in line before one of the barrels of the telescopes, near a brilliant electric light.
"What do you see, Walter?" he asked, indicating an eyepiece.
I looked. "A series of lines," I replied. "What is it?"
"That," he explained, "is a spectroscope, and those are the lines of the absorption spectrum. Each of those lines, by its presence, denotes a different substance. Now, on the pavement of the Phelps mausoleum I found, you will recall, some roundish spots. I have made a very diluted solution of them which is placed in this tube.
"The applicability of the spectroscope to the differentiation of various substances is too well known to need explanation. Its value lies in the exact nature of the evidence furnished. Even the very dilute solution which I have been able to make of the material scraped from these spots gives characteristic absorption bands between the D and E lines, as they are called. Their wave-lengths are between 5774 and 5390. It is such a distinct absorption spectrum that it is possible to determine with certainty that the fluid actually contains a certain substance, even though the microscope might fail to give sure proof. Blood—human blood—that was what those stains were."
He paused. "The spectra of the blood pigments," he added, "of the extremely minute quantities of blood and the decomposition products of hemoglobin in the blood are here infallibly shown, varying very distinctly with the chemical changes which the pigments may undergo."
Whose blood was it? I asked myself. Was it of some one who had visited the tomb, who was surprised there or surprised some one else there? I was hardly ready for Kennedy's quick remark.
"There were two kinds of blood there. One was contained in the spots on the floor all about the mausoleum. There are marks on the arm of Dana Phelps which he probably might say were made by the teeth of my police-dog, Schaef. They are human toothmarks, however. He was bitten by some one in a struggle. It was his blood on the floor of the mausoleum. Whose were the teeth?"
Kennedy fingered the now set impressions, then resumed: "Before I answer that question, what else does the spectroscope show? I found some spots near the coffin, which has been broken open by a heavy object. It had slipped and had injured the body of Montague Phelps. From the injury some drops had oozed. My spectroscope tells me that that, too, is blood. The blood and other muscular and nervous fluids of the body had remained in an aqueous condition instead of becoming pectous. That is a remarkable circumstance."
It flashed over me what Kennedy had been driving at in his inquiry regarding embalming. If the poisons of the embalming fluid had not been injected, he had now clear proof regarding anything his spectroscope discovered.
"I had expected to find a poison, perhaps an alkaloid," he continued slowly, as he outlined his discoveries by the use of one of the most fascinating branches of modern science, spectroscopy. "In cases of poisoning by these substances, the spectroscope often has obvious advantages over chemical methods, for minute amounts will produce a well-defined spectrum. The spectroscope 'spots' the substance, to use a police idiom, the moment the case is turned over to it. There was no poison there." He had raised his voice to emphasise the startling revelation. "Instead, I found an extraordinary amount of the substance and products of glycogen. The liver, where this substance is stored, is literally surcharged in the body of Phelps."
He had started his moving-picture machine.
"Here I have one of the latest developments in the moving-picture art," he resumed, "an X-ray moving picture, a feat which was until recently visionary, a science now in its infancy, bearing the formidable names of bioröntgenography, or kinematoradiography."
Kennedy was holding his little audience breathless as he proceeded. I fancied I could see Anginette Phelps give a little shudder at the prospect of looking into the very interior of a human body. But she was pale with the fascination of it. Neither Forden nor the nurse looked to the right or to the left. Dana Phelps was open-eyed with wonder.
"In one X-ray photograph, or even in several," continued Kennedy, "it is difficult to discover slight motions. Not so in a moving picture. For instance, here I have a picture which will show you a living body in all its moving details."
On the screen before us was projected a huge shadowgraph of a chest and abdomen. We could see the vertebræ of the spinal column, the ribs, and the various organs.
"It is difficult to get a series of photographs directly from a fluorescent screen," Kennedy went on. "I overcome the difficulty by having lenses of sufficient rapidity to photograph even faint images on that screen. It is better than the so-called serial method, by which a number of separate X-ray pictures are taken and then pieced together and rephotographed to make the film. I can focus the X-rays first on the screen by means of a special quartz objective which I have devised. Then I take the pictures.
"Here, you see, are the lungs in slow or rapid respiration. There is the rhythmically beating heart, distinctly pulsating in perfect outline. There is the liver, moving up and down with the diaphragm, the intestines, and the stomach. You can see the bones moving with the limbs, as well as the inner visceral life. All that is hidden to the eye by the flesh is now made visible in striking manner."
Never have I seen an audience at the "movies" so thrilled as we were now, as Kennedy swayed our interest at his will. I had been dividing my attention between Kennedy and the extraordinary beauty of the famous Russian dancer. I forgot Anginette Phelps entirely.
Kennedy placed another film in the holder.
"You are now looking into the body of Montague Phelps," he announced suddenly.
We leaned forward eagerly. Mrs. Phelps gave a half-suppressed gasp. What was the