The magistrates were now deeply attentive. They were no longer simply listening to the despised utterances of a mere scientific expert. The cast lay before them with the two footprints side by side; the evidence appealed to their own senses and was proportionately convincing.
"This is very singular," said the chairman; "but perhaps you can explain the discrepancy?"
"I think I can," replied Thorndyke; "but I should prefer to place all the facts before you first."
"Undoubtedly that would be better," the chairman agreed. "Pray proceed."
"There was another remarkable peculiarity about these footprints," Thorndyke continued, "and that was their distance apart--the length of the stride, in fact. I measured the steps carefully from heel to heel, and found them only nineteen and a half inches. But a man of Hearn's height would have an ordinary stride of about thirty-six inches--more if he was walking fast. Walking with a stride of nineteen and a half inches he would look as if his legs were tied together.
"I next proceeded to the Bay, and took two moulds from the footprints of the man with the nailed shoes, a right and a left. Here is a cast from the mould, and it shows very clearly that the man was walking backwards."
"How does it show that?" asked the magistrate.
"There are several distinctive points. For instance, the absence of the usual 'kick off' at the toe, the slight drag behind the heel, showing the direction in which the foot was lifted, and the undisturbed impression of the sole."
"You have spoken of moulds and casts. What is the difference between them?"
"A mould is a direct, and therefore reversed, impression. A cast is the impression of a mould, and therefore a facsimile of the object. If I pour liquid plaster on a coin, when it sets I have a mould, a sunk impression, of the coin. If I pour melted wax into the mould I obtain a cast, a facsimile of the coin. A footprint is a mould of the foot. A mould of the footprint is a cast of the foot, and a cast from the mould reproduces the footprint."
"Thank you," said the magistrate. "Then your moulds from these two footprints are really facsimiles of the murderer's shoes, and can be compared with these shoes which have been put in evidence?"