“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 that bubble comes from the wake of the House-boat?”
“By my chemical knowledge, merely,” replied Holmes. “A merely worldly vessel leaves a phosphorescent bubble in its wake. That one we have just discovered is not so, but sulphurescent, if I may coin a word which it seems to me the English language is very much in need of. It proves, then, that the bubble is a portion of the wake of a Stygian craft, and the only Stygian craft that has cleared the Cimmerian Harbor for years is the House-boat—Q.E.D.”
“We can go back until we find the ripple again, and follow that, I presume,” sneered Le Coq, who did not take much stock in the theories of his great rival, largely because he was a detective by intuition rather than by study of the science.
“You can if you want to, but it is better not to,” rejoined Holmes, simply, as though not observing the sneer, “because the ripple represents the outer lines of the angle of disturbance in the water; and as any one of the sides to an angle is greater than the perpendicular from the hypothenuse to the apex, you’d merely be going the long way. This is especially important when you consider the formation of the bow of the House-boat, which is rounded like the stern of most vessels, and comes near to making a pair of ripples at an angle of ninety degrees.”
“Then,” observed Sir Walter, with a sigh of disappointment, “we must change our course and sail for Paris?”
“I am afraid so,” said Holmes; “but of course it’s by no means certain as yet. I think if Columbus would go up into the mizzentop and look about him, he might discover something either in confirmation or refutation of the theory.”
“He couldn’t discover anything,” put in Pinzon. “He never did.”