Thorndyke ruled off the last line, remarking: "Then your covered way is
on the south side of a street which bears north-east. So we complete our
chart. Just look at your route, Jervis."

He held up the board with a quizzical smile and I stared in astonishment
at the chart. The single line, which represented the route of the
carriage, zigzagged in the most amazing manner, turning, re-turning and
crossing itself repeatedly, evidently passing more than once down the
same thoroughfares and terminating at a comparatively short distance
from its commencement.

"Why!" I exclaimed, the "rascal must have lived quite near to
Stillbury's house!"

Thorndyke measured with the dividers the distance between the starting
and arriving points of the route and took it off from the scale.

"Five-eighths of a mile, roughly," he said. "You could have walked it in
less than ten minutes. And now let us get out the ordnance map and see
if we can give to each of those marvellously erratic lines 'a local
habitation and a name.'"

He spread the map out on the table and placed our chart by its side.

"I think," said he, "you started from Lower Kennington Lane?"

"Yes, from this point," I replied, indicating the spot with a pencil.

"Then," said Thorndyke, "if we swing the chart round twenty degrees to
correct the deviation of the compass, we can compare it with the
ordnance map."

He set off with the protractor an angle of twenty degrees from the
north and south line and turned the chart round to that extent. After
closely scrutinizing the map and the chart and comparing the one with
the other, he said:

"By mere inspection it seems fairly easy to identify the thoroughfares
that correspond to the lines of the chart. Take the part that is near
your destination. At nine twenty-one you passed under a bridge, going
westward. That would seem to be Glasshouse Street. Then you turned
south, apparently along the Albert Embankment, where you heard the tug's
whistle. Then you heard a passenger train start on your left; that would
be Vauxhall Station. Next you turned round due east and passed under a
large railway bridge, which suggests the bridge that carries the Station
over Upper Kennington Lane. If that is so, your house should be on the
south side of Upper Kennington Lane, some three hundred yards from the
bridge. But we may as well test our inferences by one or two
measurements."

"How can you do that if you don't know the exact scale of th