of our discovery.
“What is the old gentleman like? Can you describe him?” I inquired. No doubt she took me for a detective, but at that moment this thought did not occur to me.
“He is sixty, I should think, old and decrepit, with white hair, and always walks with a stick.”
“And the lady was his daughter?” suggested the inspector.
“I suppose her to be his daughter,” she answered. “The old man’s name is Dawson, I believe – at least one day a messenger-boy brought a note here by mistake, addressed to Professor Dawson. The daughter is a very good pianist, and plays every morning regularly.”
“They are well off, as far as you can judge?” Patterson inquired with his assumed careless air.
“No, I don’t think they are, because my maid heard at Boucher’s – the grocer’s across the way – that they owed a large bill which they couldn’t settle. Again, people who have a house of that sort do not have coal by the hundredweight taken down into the kitchen as they do.”
Patterson nodded. No more sure sign of a light purse is there than the purchase of coal by the half-sack. Yet the interior of that house, with its well-laid dinner-table, certainly did not betray any sign of poverty. Indeed, I had noticed in the cellar a dusty stock of choice wines, hocks, ports, and champagnes of expensive brands.
“You don’t know the young lady’s name, then?” asked my friend, after a slight pause.
“If she’s really his daughter it would, I suppose, be Dawson,” she replied with a smile. “But I’m not certain, remember, as to either of their names.”
“Perhaps your servants may know something about them. Servants generally gossip and pick up information about one’s neighbours, you know.”
“You are right,” answered the affable old lady, “they gossip far too much. Unfortunately, however, both my servants are out at this moment.”
We chatted on, but it was evident from her conversation that her servants knew little beyond what she did. One statement she made was somewhat curious. She alleged that a few nights before she was awakened about two o’clock in the morning by hearing the loud shrill screams of a woman who seemed to be in the room next hers in the adjoining house. She could hear a man’s voice talking low and gruffly, and three or four times were the screams repeated, as if the woman were in excruciating pain.
“What visitors came to the house?” Patterson asked at length.
“Very few. A youngish gentleman came sometimes. He called the other morning just as I was going out.”
“Who admitted him?”
“The young lady herself.”
Many more questions Patterson put to the old lady, but elicited no noteworthy fact, except that two large, heavy trunks had been sent away by Parcels Delivery a couple of days before. Therefore, thanking Mrs Luff, who, of course, was extremely curious to know why the police were taking such an active interest in her neighbour, we left and made inquiries of the people in the adjoining house on the opposite hand.
It was a lodging-house and the owner, a rather surly old widow, was not at all communicative. What she told us amounted practically to what we had already learnt. She, too, had long ago set the old man and his daughter down as mysterious persons, and her two servants had never been able to find out anything regarding them.
So after nearly half an hour’s absence we returned to the house of mystery, watched, of course, by the persons in the houses on either side. None suspected a tragedy, but all remained at their windows expecting to see somebody arrested.
In the dining-room we found Doctor Knowles, the police divisional surgeon, who had been sent for by the police. He had already examined the bodies and was on the point of returning home.
“Well, doctor, what’s your opinion?” asked Patterson.
“I can form none until after the post-mortem,” answered the prim, youngish, dark-moustached man in silk hat and frock coat, a typical Kensington practitioner, who was known to be a great favourite with his lady patients.
“Are there no marks of violence?”
“None,” he responded. “Although there seems no doubt that there has been foul play, yet the means used to encompass their death remains an entire mystery. That laboratory, too, is a very remarkable feature.”
“Why?” I asked.
“Because the occupant of that place has made a discovery for which scientists have for years striven in vain,” the doctor replied.
“What is it?”
“You noticed those strange globes with the coil of tubing,” he said. “Well, from what I’ve found, it seems that the experimenter has invented a means for the liquefaction of hydrogen in large quantities.”
“Is that anything very remarkable?” I asked, in my ignorance of recent science.
“Remarkable!” he echoed. “I should rather say it was. The discovery will create the greatest interest in the scientific world. Other gases have all been handled as true liquids in measurable quantities, while until now hydrogen has only been seen in clouds or droplets, and never collected into a liquid mass. Upstairs, however, there is actually a glass bowl of liquid hydrogen. The experimenter, whoever he is, has determined at last the exact temperature at which it will liquefy, and thus a field for quite new researches, as also for new generalisations, has been thrown wide open.”
“But why is the discovery so very important?” I asked, still puzzled at the doctor’s unusual enthusiasm.
“Briefly, because by it physicists and chemists can henceforward obtain temperatures lying within thirty-five degrees from the so-called absolute zero of temperature – minus 459 degrees Fahrenheit. A possibility is thus given to study physical bodies in the vicinity of that point, which represents, so to say, the death of matter – that is, absence of the molecular vibrations which we describe as heat.”
This explanation, technical though it was, interested me. I knew Doctor Lees Knowles to be a rising man, and when reporting lectures at the Royal Institution had often noticed him among the audiences. There was no doubt that he was highly excited over the discovery, for, like myself, he had seen the liquid hydrogen boiling without any visible heat. In the papers there had been lots about Professor Dewar’s experiments in the liquefaction of oxygen, fluorine and the newly-discovered helium, and I remembered how all his efforts to bring hydrogen to a liquid state had failed. Now, however, the mysterious occupier of that house had succeeded, and every known gas could now be liquefied.
“But the murder,” observed Patterson, his thoughts reverting to the crime, for to him the most wonderful scientific discovery was as naught. “Can you form absolutely no opinion as to how it was accomplished?”
The doctor shook his head.
“There is nothing whatever to account for their sudden death, as far as I can observe,” he answered. “To the woman, however, death must have come instantly, while the man must have fallen and expired a few seconds later. There seem many mysterious features in the affair.”
“The discoverer of this latest scientific fact is undoubtedly the old man who is absent, the father of the dead girl. From him we may learn something to lead us to form conclusions,” I suggested.
“An old man!” echoed Dr Knowles. “Tell me about him.”
Briefly Patterson related all that had been told us by the neighbours, and when he had finished the doctor exclaimed —
“Then I can tell you one thing which is proved undoubtedly. The old man seen to go in and out was in reality a young one, for while looking over the laboratory I came across a white wig and a make-up box, such as is used by actors. Go upstairs and you’ll find a complete disguise there – broadcloth coat, pepper-and-salt trousers baggy at the knees, old-fashioned white vest, and collars of antique pattern.”
“Surely that can’t be true!” Patterson exclaimed in amazement.
“It