. Challenger; the life of a survey ship. Challenger; Hydrographic surveying. ATOLLS 223 tail like pieces of a jig-saw to form the picture of the atoll structure. Doctor Gaskell has described this work in scientific papers and has voiced his propositions at learned symposiums with a wealth of detail which baffles the layman, but a few weeks after the visit to the Ellice Islands he gave the Challengers, in an article in the ship's magazine, a simple account of the results of these experi- ments. At Funafuti, he said, they had found a depth of i8oo feet of rock in which the velocity of sound was
. Challenger; the life of a survey ship. Challenger; Hydrographic surveying. ATOLLS 223 tail like pieces of a jig-saw to form the picture of the atoll structure. Doctor Gaskell has described this work in scientific papers and has voiced his propositions at learned symposiums with a wealth of detail which baffles the layman, but a few weeks after the visit to the Ellice Islands he gave the Challengers, in an article in the ship's magazine, a simple account of the results of these experi- ments. At Funafuti, he said, they had found a depth of i8oo feet of rock in which the velocity of sound was 6000—8000 feet per second, such a velocity being much as one would expect in coral limestone. Below this lay material with a velocity of sound of ——— Sea level Speed of Sound eoOO - 8000 Hard Vvlcanic core Structure of Funafuti Atoll as deduced from seismic experiment 12,000 feet per second, which could either be hard limestone or volcanic rock. To clear up the matter he had carried the explo- sions in Nukufetau right up to the edge of the reef and these showed that the border between these two layers fell rapidly away as the perimeter was reached, which gave a picture of a supposed volcanic hump within the heart of the atoll structure. Deeper again an even harder material was located, probably the true volcanic core of the original volcano which had formed the island. Thus, on the seismic evidence obtained by Challenger it would seem that as the coral cannot live at a depth greater than 200 feet below the surface of the ocean, the atolls forming the Ellice. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ritchie, G. S. (George Stephen), 1914-. New York, Abelard-Schuman
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Keywords: ., bookcentury1900, bookcollectio, booksubjecthydrographicsurveying
