She paused and for the first time showed a moment’s difficulty in continuing her story. Then she resumed.
“Last Sunday, after Evensong, the sexton and the rector went up the tower in the dusk to light the lantern. Twilight was coming on but it was not quite dark. A mist was gathering with the incoming tide, coming down like a curtain across the shore. It had not quite reached the level of the marsh. As the two men began to climb the stone steps of the winding stairs, they heard a gunshot.”
“A shot of what kind?”
“A shotgun, Mr Holmes, fired from somewhere on the marshes. It is not uncommon by daylight but unusual in the dusk, except as a signal. By the time the two men came out on to the lead of the flat roof, the incoming tide was running fast, as it does across the mud-banks. The narrowing of the estuary channels it in. Yet the worst of it, Mr Holmes, is that the marsh and the mudflats may look level but they seldom are. You may stand on a stretch of uncovered sand, where the sea is a hundred yards out, and you may think yourself safe. But the ripples have outflanked you. Your retreat is already cut off by the depth of water gathering at your back or by the softness of the flats where the tide has percolated below, undermining the firmness and turning it into quicksand. Then the sea comes rushing in on either side of you, sometimes as fast as a man can run. All this is a hundred times worse in the dusk. You see?”
“Entirely.”
“Anyone on the marsh or the flats by that time last Sunday evening was in peril. The sexton lit the beacon at once. The Old Light was already flashing. Then Mr Gilmore, the rector, and the sexton saw two men on the soft mud, below the mist that was coming with the tide. It was so far off that, with daylight fading, it was hard to tell who they were. But it seemed that they were fighting. One man appeared to seize the other and they fell together. The second man got up and ran off but the first caught him and threw him down again. Or so it seemed. The dusk thickened and the mist drew round them but a struggle of some kind went on. The mud was so soft and so slippery and they fell so often that, if there was a fight, neither seemed able to win it. There was nothing that the rector and the sexton on the roof of the tower could do, even at the risk of their own lives. They were too far off.”
“Did they think, perhaps, that these were two young fellows playing the fool?” I asked.
“No man who knew the sands would do so in such a place, Dr Watson.”
“Very well.”
“They were too far away by that time for Mr Gilmore or the sexton even to tell their ages. Yet, since then, neither of my brothers has been seen. It was the following morning, after the tide turned, that two policemen went to the Old Light. A Tynemouth collier, at anchor across the water, had seen the beam of the Old Light fail an hour or so before dawn. When I came from Mablethorpe, they helped me to climb the ladder and I was able to get into the barrack-room. There lay the letter in the table drawer.”
Now that she had come to the true end of her story, there was a moment’s silence, broken by Holmes.
“And there was nothing else that you noticed when you went into the barrack-room next day?”
“Abraham’s jacket was hanging behind the door. I went through the pockets. There was a piece of a pebble in one pocket.”
“What sort of pebble?”
“I should not have bothered with it—I should not even have noticed it—except that he had folded it carefully in a piece of paper. I thought at first that the paper might have a message on it. There was none, only a pebble.”
“Where is it now?”
“I took it with me. It could not possibly be of use to the police.”
“I fear you may be in error as to that, Miss Chastelnau. Do you have it with you now?”
She reached into the pocket of her dress and took out the folded paper which, as she had said, was quite blank. I got up and stood beside Holmes as he unwrapped the pebble. Before us lay what I can only describe as a small piece of clay-coated grit or possibly a rough pebble from the shoreline. It was the size of my thumb-nail, certainly no larger.
Holmes stared at it for a moment longer and then again spoke slowly to our client, as I may now call her.
“With your permission, Miss Chastelnau, I should like to retain this item for a few hours in order to examine it. You must return to Mablethorpe tonight, I believe. We shall see you safely to King’s Cross station. You may depend upon Dr Watson and I being in Sutton Cross by noon tomorrow. I will bring the pebble with me then. I fear that I cannot assure you what the outcome of this mystery will be. However, from what you have told us, I have every confidence that the riddle of your brothers’ disappearance will be resolved within the next three days.”
“Of what possible use to you can a muddy pebble be?”
“Had it not been wrapped with such care, I should probably have thought it of no use whatever. However, such careful treatment reminds me that this is hard stone, though it came apparently from a bed of soft clay to which it did not belong. I do not call that conclusive of anything—but in the light of all the other evidence it is suggestive of something.”
2
T
hat evening, after we had seen Miss Chastelnau safely to her train, Sherlock Holmes ate his dinner from a tray beside him on his work-table. The table’s disreputable surface was stained by hydrochloric acid and the results of numerous chemical “experiments.” Scattered upon it now lay a lens and a pair of forceps, a stained penknife in a butter-dish, and a medical scalpel. A dismembered revolver had awaited his attention for two or three weeks. Close at hand were two skulls, whose owners had been hanged for murder at Tyburn a century ago and publicly dissected before a large public audience at Surgeons Hall. These two macabre fetishes now acted as book-ends for a brief row of well-thumbed reference volumes, required for immediate purposes. My friend had exchanged his formal black coat for the familiar purple of his dressing-gown.
It was after ten o’clock and his long back was curved once again over the Chastelnau pebble, as I had better call it. He had been examining it for several minutes by the aid of a jeweller’s lens screwed into his eye. Removing this eyepiece, he straightened in his chair.
“I believe we can do better, Watson. We are no common high street supplier of watches and
bijouterie.”
He had scarcely spoken a word since we had returned from escorting our visitor to King’s Cross Station and he had certainly not invited conversation in the half hour since our return. Rising from his chair, he now went across to his “natural sciences” cupboard and drew out a piece of apparatus. This was a hydroscopic balance, cased in mahogany and stamped along its base in gold, “E. Dertling, London.” He sat down and placed it in front of him.
The device resembled an open-sided box of polished wood about ten inches in height, twelve inches long and six inches deep. Within it, the pivot of a brass balance was screwed to the centre of its floor. A minute weighing pan was suspended to either side of this. From the lower edge of the box protruded a small brass knob for the alignment of the scales. This had been calibrated to calculate weights to within one milligram.
“I believe we may allow for a room temperature of sixty degrees Fahrenheit, Watson. Would that be your guess?”
This was conversation at last.
“Certainly no lower than that, with the fire glowing as it is and the curtains closed.”
Holmes took Miss Chastelnau’s pebble. With a fine brush he worked over its surface to displace any loose substance that might still have adhered to it. Then, placing it in a loop of thin wire which was suspended from the pan on the right hand of the balance, he adjusted the mechanism and noted the weight of it in air. Next, taking the pebble with a pair of tweezers, he placed a small jar of water under the right-hand scale-pan, so that when he lowered the pan the pebble was immersed. Almost as an afterthought, he dipped the slender brush into the jar and went over the stone again, apparently to dislodge any bubbles of air which might give buoyancy to so small an object.
As I watched the intensity with which my friend worked I could not help thinking that Sherlock Holmes seemed less like the great consulting detective of Baker Street than a like happy child on Christmas Morning. Perhaps there was a slighter difference between the two types than I had supposed. Now he took his brass propelling pencil and made several notes on the immaculate starch of his white shirt cuffs. At length he had his answer.
“If our estimate of the room temperature is correct, Watson—and I do not think we can be far out—the specific gravity of this mineral is registered as 3.993. I do not believe it can be andradite, for I have tried it judiciously with a penknife and that will not produce a scratch upon it. Nor, I think can it be zircon of whatever type. I therefore deduce that what we are presented with appears to be a species of corundum. Only caborundum and the diamond are harder than this. Indeed, in the scale of hardness drawn up by the admirable Professor Friedrich Mohs in 1812, only the diamond exceeds it. This cannot possibly be a diamond for its specific gravity is far too high. That I believe is as far as we can go for the present.”
Holmes had given me the opportunity I had been looking for. I had not wished to annoy him or to suggest that a piece of grit picked up from the Lincolnshire fens was unlikely to be of any value or relevance to the case whatever. However, I had been thinking wistfully of sleep. A long journey lay ahead in the morning. I yawned, stretched, made my excuses and withdrew to bed.
I suppose it was about half-past eleven when my head touched the pillow. I was woken after several hours by a dreadful screaming. It might have been a banshee—or at least the sound which I had always assumed a banshee would make. I sat up with heart pounding and, at the same time, a sense of considerable irritation.
By the time I had lit a candle, the high-pitched sound came again. It was a demented shrieking from somewhere below me. Now that I was fully awake, I recognised that whatever its origins, they were mechanical and not animal. The time by my watch was ten minutes past three in the morning. It was plain that Sherlock Holmes had not yet gone to bed.
I had not the least doubt that this disturbance would be heard on every floor of the house, and more importantly throughout those of the houses on either side. Pulling on my dressing-gown, I tied its belt and made my way by candlelight to the stairs. I began to descend to our sitting-room. Half-way down, I was aware of a lone figure on the little chair outside the door of that room. The flickering candle showed me Mrs Hudson. She was wrapped in a shawl round her nightdress, rocking to and fro a little. With her face buried in her hands she uttered a repeated protest that was almost a dry sob.
“Oh, that noise! Oh, that dreadful, dreadful noise! Why will he not stop?”
She looked up and saw me with a candlestick in my hand, standing at the top of the staircase like Banquo’s ghost on the stage of the Lyceum Theatre.
“Oh, Dr Watson! None of my gentlemen, in all these years, has ever been such a trial as Mr Holmes! What am I to do? What am I to say tomorrow morning to Mrs Armitage next door?”
“This is too bad,” I said soothingly, “Go back to bed, Mrs Hudson, and leave this to me. I promise you that the noise will stop.”
I was becoming more impatient with every moment of delay. I tried the handle of the sitting-room door and found it locked. I hammered on the oak panel with all the majesty of the law. There was a pause in the din. I sensed Holmes coming towards me and a key rattled in the lock. He flung open the door and almost pulled me into the room, his eyes gleaming. I now saw that he had screwed his carborundum wheel to the edge of the work-table and that it was the friction of its hard grey stone cleaning a penknife blade that had caused the din. The wheel had apparently also been at work upon Miss Chastelnau’s pebble. On one side of the dun-coated stone was now revealed what looked like a dull speck of royal blue glass.
“Corundum, Watson! The stuff of rubies and sapphires. A blue sapphire fit for the crown of England! Lost in the muddy dullness of time and neglect! After I heard the good lady’s story, I suspected that something like this must be the truth, though I hardly dared to believe it. Once we had been given a specific gravity of 3.993, I was certain. The figure is sometimes a fraction higher but the room temperature would account for that.”
“Corundum?”
“Corundum yields the ruby or the sapphire, according to the form of its crystals. In white light, the ruby absorbs every shade but red and therefore it glows red. Sapphire reflects only blue, as in this case. Take the jeweller’s glass and look. You will observe that the crystals are quite clearly tall and pointed, as in the sapphire, and not shorter and rectangular as in the ruby.”
“It looks very little like a jewel to me.”
“Nor should it after so many centuries in the earth. That is something which skilled polishing will amend in due course.”
“But not tonight, unless you want Mrs Hudson to throw both of us out into the street.”
He chuckled, as if in a fit of mischief.
“Not tonight, then. We know enough now to put us on the track. Tomorrow will be soon enough to prove that we are right.”
“Meantime we are to assume that the Chastelnau brothers have been made away with for such a miserable little object as this?”