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Rh says was lent “gratuitously” to me —was paid for in February, 1874, and two others are at this moment on their way from New York to England. Both by word and deed have we acknowledged our real obligations to the United States; but what we did not and could not acknowledge (for it was non-existent) was, any solution of the conflicting and anomalous results obtained with these fog-signals—results so conflicting and so anomalous as to cause reflecting minds to entertain doubts as to the capacity of the observers. Apart from the friendship shown to me at the time, all that I remember of the meeting at Washington, to which your critic refers, is the utter perplexity of everybody present, myself included, in regard to the matter in hand. I had my guess—others had theirs; but we were quite at sea in our guesses, without a signal to guide us through the intellectual fog.

Knowing, indeed, the difficulty of the subject, when its investigation was first proposed to me by the Elder Brethren, I shrank (as Faraday had done before me) from a work of such obvious labor and such uncertain scientific promise. Doggedly, however, we attacked it, determined to go through the mechanical processes already followed by others, even if they led, as regards science, to an equally barren result. Out of the darkness at length came the dawn. We prolonged our investigations until they embraced every agent, save one, to which influence had been previously ascribed. The exception was snow. This, however, was directly met by observations made upon the Mer de Glace in the bitter winter of 1859, and which have been entirely confirmed by the later observations of General Duane. Having negatived antecedent theories, we wrought our way positively to the basis of the whole question. This we found in a cloud-world, invisible to the eye of sense, but as visible and certain to the mental eye as the ordinary cloud-world of our atmosphere. The lights and shadows of these “acoustic clouds”—the action of which must, at one time or another, have been noticed by every peasant within range of a peal of bells—sufficed to account for the most astounding variations of intensity. This, I say, has been established, not only by patient and long-continued observations afloat, but by laboratory experiments as indubitable as any within the range of physical science.

And, let me add, it was neither whistles nor trumpets, nor yet the siren, which pointed out the way to this solution, but experiments with guns ably served by artillerymen from Dover Castle.

I will not make any further draft upon your generosity, though, were it worth while to do so, other fallacies of fact and logic in your critic's article might be exposed. He says, or intimates, for example, that I became “adviser” to the Trinity House after my “lecturing tour in the United States in 1873.” I relieved Michael Faraday of this duty in May, 1866. My friends in New York have already had