As the weight fell upon the step it gave way so slightly as to be almost imperceptible, but suddenly from hidden cavities around the well-like shaft there came six rings of long, sharp steel spikes, set inwards, three above and three below, which, contracting as they came forward, met and interlaced. In an instant I recognised what terrible fate would be the lot of any adventurer who dared to enter that dark shaft. The action of stepping upon that fatal projecting iron released hydraulic pressure of irresistible power, and the unfortunate one, unable to ascend or descend by reason of the danger being above and below, must be impaled by a hundred cruel spikes, sharp and double-edged like spears, while the bands whereon they were set must crush his bones to pulp.
I looked at this terrible device for producing an agonizing death and shuddered. The precautions taken to prevent anyone entering the place were the most elaborate and ingenious I had ever seen. Even if any person learnt the secret of draining the lake, the shaft leading to the mysterious subterranean place was unapproachable by reason of this extraordinary mechanical device.
During five minutes the spikes remained interlaced, then automatically they disengaged themselves, and slowly fell back into the cavity running round the brickwork, wherein they remained concealed.
Thrice again did Omar repeat this action of pressing the bar upon the step, each time with an exactly similar result, chatting to me the while. Then, when for the third time the spikes had fallen back into their places, he said:
"Now the secret to avoid this and lock the mechanism is to turn back this little lever and place it in this catch, so. This cannot, however, be done unless the step has been pressed three times."
And bending over he showed me another tiny lever thickly encrusted with rust, secreted behind a movable brick in the first tier below the lake's bottom. This he placed in position, securing it in a niche so that it became immovable.
"Now," he said, "we may descend without fear," and with these words knelt down, and after lighting a torch he had brought with him, commenced the descent into the cavernous gloom. I quickly followed, my feet resting for a brief instant upon the fatal iron projection, but no spikes came forward, for the terrible mechanism was now locked. Deep down into this circular shaft we went, the smoke and sparks from Omar's torch ever ascending into my face as I lowered myself from rung to rung, until at last, at considerable depth, we found ourselves in a kind of natural cavern. The place seemed damp and full of bad odours, to which submitting with patience we, by a long passage, sometimes crawling under rugged arches, sometimes wading in mud and dirt, attained the end of the cavern, where we stumbled on some narrow steps; but the torch shed little light, and we became nearly suffocated by the noisome vapours.
"I thought you said the air was fresh here," I exclaimed good-humouredly to my companion.
"So I did," he answered. "I cannot make out why it has become so foul. The air-holes must have become accidentally stopped up."
The widening ascent was so intricate and clogged with dirt and rubbish that we worked like moles in the dark; nevertheless, by diligent industry we gained ground considerably, yet as we endeavoured to mount, the slimy steps slipped from under us, and ever and anon we would come tumbling down with a weight of dirt upon us.