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Page 29 - As I stood upon the deck of the 'Irene' pondering this question, I became conscious of the exceeding power of the sun beating against my back and heating the objects near me. Beams of equal power were falling on the sea, and must have produced copious evaporation. That the...
Page 32 - The instruments, hidden from view, were ou the summit of a cliff 235 feet above us, the sea was smooth and clear of ships, the atmosphere was without a cloud, and there was no object in sight which could possibly produce the observed effect. From the perfectly transparent air the echoes came, at first with a strength apparently but little less than that of the direct sound, and then dying gradually and continuously away.
Page 260 - The undersigned, envoy extraordinary and minister plenipotentiary of the United States of America, has the honor to acknowledge the receipt of...
Page 58 - Now it frequently occurs that a signal, which under ordinary circumstances would be audible at the distance of fifteen miles, cannot be heard from a vessel at the distance of a single mile. This is probably due to the reflection mentioned by Humboldt. The temperature of the air over the land where the fog-signal is located, being very different from that over the sea, the sound — in passing from the former to the latter, undergoes reflection at their surface of contact. The correctness of this...
Page 37 - II., a fixed disk and a rotating disk are employed, but radial slits are used instead of circular apertures. One disk is fixed vertically across the throat of a conical trumpet...
Page 28 - ... does not possess the molecular continuity of the crystal, but is a mere aggregate of minute grains not in perfect optical contact with each other. Where this is the case a portion of the heat is always reflected on entering and on quitting a grain ; hence when...
Page 28 - Thus, by the mixture of air and ice, two transparent substances, we produce a substance as impervious to light as a really opaque one. The same remark applies to foam, to clouds, to common salt, indeed to all transparent substances in powder. They are all impervious to light, not through the real absorption or extinction of the light, but through internal reflection. Humboldt, in his observations at the Falls of the Orinoco, is known to have applied these principles.
Page 32 - Edwards, who was good enough on this and some other days to act as my amanuensis, at 1 PM I was rowed to the shore, and landed at the base of the South Foreland Cliff. The body of air which had already shown such extraordinary power to intercept the sound, and which manifested this power still more impressively later in the day, was now in front of us.