Page:Austin Freeman - The Mystery of 31 New Inn.djvu/178

 "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 traveled 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 traveling 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."

"That doesn't sound very exact as to distance," I objected.

"It isn't. But that doesn't matter much. We have certain landmarks, such as these railway arches that you have noted, by which the actual distance can be settled after the route is plotted. You had better read out the entries, and, opposite each, write a number for reference, so that we need not confuse the chart by writing details on it. I shall start near the middle of the board, as neither you nor I seem to have the slightest notion what your general direction was."

I laid the open notebook before me and read out the first entry:

"'Eight fifty-eight. West by South. Start from home. Horse thirteen hands.'"