SKEATS: CHEMICAL COMPOSITION OF LIMESTONES. 91 
the sea cliff the ground rises rather sharply to a height of 880 feet, and 
an analysis made at that level (No. 514) yields 40.67 per cent of mag- 
nesium carbonate, while some distance to the south-west (No. 1011), 
at a height of 800 feet, is also dolomitic containing 35.2 per cent of 
magnesium carbonate. 
Calcium Magnesium 
Number. Height. Carbonate. Carbonate. 
663 750’ 98.3 17. 
657 710’ 97.5 2.5 
658 a 710’ 97.5 2.5 
658 B 710’ 60.5 39.5 
514 880’ 59.33 . 40.67 
1011 860’ 64.8 35.2 
Microscopical. No. 658 a.— The rock consists of small fragments of 
well-preserved organisms, such as Carpenteria, Lithothamnion, etc., set 
in a gray silty calcite matrix. The rock is probably a recrystallized 
calcareous “ mud.” 
No. 6588. The slide consists almost entirely of idiomorphic crystals 
of dolomite, having dark centers. Most of the organisms have been 
obliterated, but one or two specimens of Amphistegina, and possibly 
Polytrema, occur. In some places scalenohedral crystals project from the 
surfaces of organic fragments. 
No. 514. The section consists largely of rhombohedra of dolomite, in 
many of whose centers are dark materials caught up in an early stage of 
crystallization, and hence giving the appearance of zoning. All organ- 
isms have disappeared, except possibly where a meandrine arrangement 
of opaque or silty matter may represent a former organism, such as coral 
or Polytrema. 
No. 1011. A dolomitic limestone in which many of the crystals have 
dark centers. Some spaces in the rock have, since dolomitization, been 
filled with secondary calcite. 
SouTHEAsT oF PHospHate Hitu. — The section of the older rocks at 
this spot is not complete. The upper 200 feet is clear, and at one place 
near the shore, erosion has caused the Eocene or Oligocene limestones 
to be exposed below a bed of basalt. Between these points three ter- 
races or fringing reefs occur, and mask the older rocks. The average 
slope of the cliffs towards the sea is about 30°. 
Chemical. — Miocene rocks are exposed from the top of the cliff at 790 
feet down to 610 feet. Analyses made between these heights show that 
the upper 120 feet consists entirely of limestones, with about 3 per cent 
of magnesium carbonate. At the level of 640 feet the percentage has 
