athway. In the middle of it,
clearly marked on the sodden soil, was the track of a bicycle.

"Hurrah!" I cried. "We have it."

But Holmes was shaking his head, and his face was puzzled and expectant
rather than joyous.

"A bicycle, certainly, but not THE bicycle," said he. "I am familiar
with forty-two different impressions left by tyres. This, as you
perceive, is a Dunlop, with a patch upon the outer cover. Heidegger's
tyres were Palmer's, leaving longitudinal stripes. Aveling, the
mathematical master, was sure upon the point. Therefore, it is not
Heidegger's track."

"The boy's, then?"

"Possibly, if we could prove a bicycle to have been in his possession.
But this we have utterly failed to do. This track, as you perceive, was
made by a rider who was going from the direction of the school."

"Or towards it?"

"No, no, my dear Watson. The more deeply sunk impression is, of course,
the hind wheel, upon which the weight rests. You perceive several places
where it has passed across and obliterated the more shallow mark of the
front one. It was undoubtedly heading away from the school. It may or
may not be connected with our inquiry, but we will follow it backwards
before we go any farther."

We did so, and at the end of a few hundred yards lost the tracks as
we emerged from the boggy portion of the moor. Following the path
backwards, we picked out another spot, where a spring trickled across
it. Here, once again, was the mark of the bicycle, though nearly
obliterated by the hoofs of cows. After that there was no sign, but
the path ran right on into Ragged Shaw, the wood which backed on to the
school. From this wood the cycle must have emerged. Holmes sat down on
a boulder and rested his chin in his hands. I had smoked two cigarettes
before he moved.

"Well, well," said he, at last. "It is, of course, possible that a
cunning man might change the tyre of his bicycle in order to leave
unfamiliar tracks. A criminal who was capable of such a thought is a man
whom I should be proud to do business with. We will leave this question
undecided and hark back to our morass again, for we have left a good
deal unexplored."

We continued our systematic survey of the edge of the sodden portion
of the moor, and soon our perseverance was gloriously rewarded. Right
across the lower part of the bog lay a miry path. Holmes gave a cry
of delight as he approached it. An impression like a fine bundle of
telegraph wires ran down the