comparatively safe for a while at least, Sherlock Holmes came down from
the bridge, where he had taken his place as the commander of the
expedition at the moment of departure. His brow was furrowed with anxiety,
and through his massive forehead his brain could be seen to be throbbing
violently, and the corrugations of his gray matter were not pleasant to
witness as he tried vainly to squeeze an idea out of them.

"What is the matter?" asked Demosthenes, anxiously. "We are not in any
danger, are we?"

"No," replied Holmes. "But I am somewhat puzzled at the bubbles on the
surface of the ocean, and the ripples which we passed over an hour or two
ago, barely perceptible through the most powerful microscope, indicate to
my mind that for some reason at present unknown to me the House-boat has
changed her course. Take that bubble floating by. It is the last expiring
bit of aerial agitation of the House-boat's wake. Observe whence it comes.
Not from the Azores quarter, but as if instead of steering a straight
course thither the House-boat had taken a sharp turn to the northeast, and
was making for Havre; or, in other words, Paris instead of London seems to
have become their destination."

Demosthenes looked at Holmes with blank amazement, and, to keep from
stammering out the exclamation of wonder that rose to his lips, he opened
his _bonbonnière_ and swallowed a pebble.

"You don't happen to have a cocaine tablet in your box, do you?" queried
Holmes.

"No," returned the Greek. "Cocaine makes me flighty and nervous, but these
pebbles sort of ballast me and hold me down. How on earth do you know that