d what we know as to this officer's proceedings, inasmuch as they
have to do with the thread of our narrative.

It may be that other motives, besides those connected with George Aspel,
induced the man in grey to visit the General Post-Office, but we do not
certainly know. It is quite possible that a whole host of subsidiary
and incidental cases on hand might have induced him to take up the
Post-Office like a huge stone, wherewith to knock down innumerable birds
at one and the same throw; we cannot tell. The brain of a detective
must be essentially different from the brains of ordinary men. His
powers of perception--we might add, of conception, reception, deception,
and particularly of interception--are marvellous. They are altogether
too high for us. How then can we be expected to explain why it was
that, on arriving at the Post-Office, the man in grey, instead of asking
eagerly for George Aspel at the Inquiry Office, or the Returned Letter
Office, or the _poste restante_, as any sane man would have done, began
to put careless and apparently unmeaning questions about little dogs,
and to manifest a desire to be shown the chief points of interest in the
basement of St. Martin's-le-Grand?

In the gratifying of his desires the man in grey experienced no
difficulty. The staff of the Post-Office is unvaryingly polite and
obliging to the public. An order was procured, and he soon found
himself with a guide traversing the mysterious regions underneath the
splendid new building where the great work of postal telegraphy is
carried on.

While his conductor led him through the labyrinthine passages in which a
stranger would infallibly have lost his way, he explained the various
objects of interest--especially pointing out the racks where thousands
on thousands of old telegrams are kept, for a short time, for reference
in case of dispute, and then destroyed. He found the man in grey so
intelligent and sympathetic that he quite took a fancy to him.

"Do you happen to remember," asked the detective, in a quiet way, during
a pause in his companion's remarks, "anything about a mad dog taking
refuge in this basement some time ago--a small poodle I think it was--
which disappeared in some mysterious way?"

The conductor had heard a rumour of such an event, but had been ill and
off duty at the time, and could give him no details.

"This," said he, opening a door, "is the Battery Room, where the
electricity is generated for th