Microscopic view of 'mud' from Challenger Report, Narrative Vol.I pt 2 plate 0 figure 6; section of a seolitic spherole. HMS Challenger made a three and a half year circumnavigation from December 1872 to May 1876. The voyage is particularly famous since it is said to mark the beginning of modern oceanography. The ship was adapted to accommodate the scientists' measurement of physical data and collection of samples from the ocean and sea floor.
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