. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 92 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. increased to 27.7, while at 610 feet no less than 42.7 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 3.9 per cent of magnesium carbonate. • Number. Height. Calcium Carbonate. Magnesium Carbonate. 610 790' 97.0 3.0 611 760' 97.3 2.7 612 730'
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. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 92 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. increased to 27.7, while at 610 feet no less than 42.7 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 3.9 per cent of magnesium carbonate. • Number. Height. Calcium Carbonate. Magnesium Carbonate. 610 790' 97.0 3.0 611 760' 97.3 2.7 612 730' 96.8 3.2 613 700' 97.1 2.9 614 670' 97.7 2.3 615 640' 72.3 27.7 616 610' 57.3 42.7 635 0' 96.1 3.9 SOUTH-EAST OF PHOSPHATE HILL. Older Rocks.. 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 39.22 per cent of magnesium carbonate, while No.. Please note that these images are extracted from scanned page images that may have been digitally enhan