"I am afraid it does. But—have you got your notes of the compass-bearings?"
"The book is in my overcoat pocket with the board. I will fetch them."
I went into the office, where our coats hung, and brought back the notebook with the little board to which it was still attached by the rubber band. Thorndyke took them from me, and, opening the book, ran his eye quickly down one page after another. Suddenly he glanced at the clock.
"It is a little late to begin," said he, "but these notes look rather alluring. I am inclined to plot them out at once. I fancy, from their appearance, that they will enable us to locate the house without much difficulty. But don't let me keep you up if you are tired. I can work them out by myself."
"You won't do anything of the kind," I exclaimed. "I am as keen on plotting them as you are, and, besides, I want to see how it is done. It seems to be a rather useful accomplishment."
"It is," said Thorndyke. "In our work, the ability to make a rough but reliable sketch survey is often of great value. Have you ever looked over these notes?"
"No. I put the book away when I came in and have never looked at it since."
"It is a quaint document. You seem to be rich in railway bridges in those parts, and the route was certainly none of the most direct, as you noticed at the time. However, we will plot it out and then we shall see exactly what it looks like and whither it leads us."
He retired to the laboratory and presently returned with a T-square, a military protractor, a pair of dividers and a large drawing-board on which was pinned a sheet of cartridge paper.
"Now," said he, seating himself at the table with the board before him, "as to the method. You started from a known position and you arrived at a place the position of which is at present unknown. We shall fix the position of that spot by applying two factors, the distance that you travelled and the direction in which you were moving. The direction is given by the compass; and, as the horse seems to have kept up a remarkably even pace, we can take time as representing distance. You seem to have been travelling at about eight miles an hour, that is, roughly, a seventh of a mile in one minute. So if, on our chart, we take one inch as representing one minute, we shall be working with a scale of about seven inches to the mile."