. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 92 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. increased to , while at 610 feet no less than per cent of mag- nesium carbonate is found. At this point the section of the older rocks is masked by terraces or fringing reefs, which form a cloak of newer material, only pierced at one point above sea-level, where an Eocene or Oligocene limestone occurs (No. 635) having per cent of magnesium carbonate. • Number. Height. Calcium Carbonate. Magnesium Carbonate. 610 790' 611 760' 612 730'
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 92 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. increased to , while at 610 feet no less than per cent of mag- nesium carbonate is found. At this point the section of the older rocks is masked by terraces or fringing reefs, which form a cloak of newer material, only pierced at one point above sea-level, where an Eocene or Oligocene limestone occurs (No. 635) having per cent of magnesium carbonate. • Number. Height. Calcium Carbonate. Magnesium Carbonate. 610 790' 611 760' 612 730' 613 700' 614 670' 615 640' 616 610' 635 0' SOUTH-EAST OF PHOSPHATE HILL. Older Microscopical. No. 610. — A limestone containing an unrolled frag- ment of Orbitoides, together with Polytrema, Amphistegina, and a little yellow isotropic material, possibly palagonite. The organisms are well preserved, the rock is cavernous, and the semi-opaque matrix is seen under the high power to be crystalline. No. 615. A very cavernous dolomite showing no traces of organisms, except a few meandrine forms. The spaces and cavities in the rock have been, to a great extent, filled with large slightly yellow crystals of secondary calcite. No. 616. A uniform, compact, fine-grained dolomite, showing a few small fragments of Lithothamnion, and here and there dark meandrine patches suggesting the former presence of Polytrema. Sydney's Dale. — This dale is a gorge on the west coast, originally determined by a fault line, and further excavated by a stream which runs through it. In this dale Oligocene or Eocene beds occur, con- taining the oldest type of Orbitoides met with at Flying Fish Cove. Cliemical. — Three limestones were analyzed : No. 308, from a height of 350 feet, contains per cent of magnesium carbonate, while Please note that these images are extracted from scanned page images that may have been digitally enhan
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