IT WAS one o’clock when we left No. 3, Lauriston Gardens. Sherlock Holmes led me to the nearest telegraph office, whence he dispatched a long telegram. He then hailed a cab, and ordered the driver to take us to the address given us by Lestrade.

“There is nothing like first-hand evidence,” he remarked; “as a matter of fact, my mind is entirely made up upon the case, but still we may as well learn all that is to be learned.”

“You amaze me, Holmes,” said I. “Surely you are not as sure as you pretend to be of all those particulars which you gave.”

“There’s no room for a mistake,” he answered. “The very first thing which I observed on arriving there was that a cab had made two ruts with its wheels close to the curb. Now, up to last night, we have had no rain for a week, so that those wheels which left such a deep impression must have been there during the night. There were the marks of the horse’s hoofs, too, the outline of one of which was far more clearly cut than that of the other three, showing that that was a new shoe. Since the cab was there after the rain began, and was not there at any time during the morning - I have Gregson’s word for that - it follows that it must have been there during the night, and therefore, that it brought those two individuals to the house.”

“That seems simple enough,” said I; “but how about the other man’s height?”

“Why, the height of a man, in nine cases out of ten, can be told from the length of his stride. It is a simple calculation enough, though there is no use my boring you with figures. I had this fellow’s stride both on the clay outside and on the dust within. Then I had a way of checking my calculation. When a man writes on a wall, his instinct leads him to write above the level of his own eyes. Now that writing was just over six feet from the ground. It was child’s play.”

“And his age?” I asked.

“Well, if a man can stride four and a half feet without the smallest effort, he can’t be quite in the sere and yellow. That was the breadth of a puddle on the garden walk which he had evidently walked across. Patent-leather boots had gone round, and Square-toes had hopped over. There is no mystery about it at all. I am simply applying to ordinary life a few of those precepts of observation and deduction which I advocated in that article. Is there anything else that puzzles you?”

“The finger-nails and the Trichinopoly,” I suggested.

“The writing on the wall was done with a man’s forefinger dipped in blood. My glass allowed me to observe that the plaster was slightly scratched in doing it, which would not have been the case if the man’s nail had been trimmed. I gathered up some scattered ash from the floor. It was dark in colour and flaky - such an ash is only made by a Trichinopoly. I have made a special study of cigar ashes - in fact, I have written a monograph upon the subject. I flatter myself that I can distinguish at a glance the ash of any known brand either of cigar or of tobacco. It is just in such details that the skilled detective differs from the Gregson and Lestrade type.”

“And the florid face?” I asked.

“Ah, that was a more daring shot, though I have no doubt that I was right. You must not ask me that at the present state of the affair.”