CORAL LIMESTONES FROM THE SOUTH SEA ISLANDS. 161 
4. Turr Rock ? 
This specimen was also collected in 1876 by Dr. Messer, 
on the island of Vati, one of the New Hebrides, from what he 
ibes as a raised terrace of coral rock, which crops out above 
Havannah Harbour, at a height of 525 feet sate sea-level, the 
highest point of the island being about 1,500 fee 
The rock is greyish white in colour and sate friable ; but, as 
be at once apparent from the an alysis, ae is nota limestone, 
although it may have been found to contain 
addition of acid it effervesces but pee showing the 
presence of only a small amount of carbonic acid. 
gers 
Hygroscopic moisture, @ 100° C 3°68 
Combined water, ta) gre iss 68 
ic acid a: OS 
ca ‘70 
A et 21:82 / 
aceite wes ees ie i | ee labia ply 
ron sesquioxide ... res i ee 
Lime eae ae : 1°66 
Magnesia ... trace. 
Potash and soda uy S. 
c iv oti ae ..» 56°56 
Alumina ... oy vide ... 14°80 78:18 
Lime bs bee im ... trace. Insoluble in 
Magnesia 6-76 acid. 
06 
100-00 
The combined water was determined by ignition of the rock 
to complete fusion; allowance was made for the carbonic acid 
which was also deren off at the same time. 
5. Turr Rock, New Hebrides. 
Brought by the late Commodore Goodenough, R.N., from the 
shore, Hei high-water-mark, of Port Sandwic h, M coll 
knif grain. 
€. a dull sound when Dare Spenifi gravity, 2° 186. 
Poa “coral sand rock,” but, as will be seen from the 
analysis, it is mainly a silicate of alumina. 
