Torres' Strait .] 
TERRA AUSTRALIS. 
115 
venient anchorage for the night to a ship passing through Torres' 
Strait : I named it Half-way Island. It is scarcely more than a mile Saturday so, 
in circumference, but appears to be increasing both in elevation and 
extent. At no very distant period of time, it was one of those banks 
produced by the washing up of sand and broken coral, of which 
most reefs afford instances, and those of Torres' Strait a great many. 
These banks are in different stages of progress : some, like this, are 
become islands, but not yet habitable ; some are above high-water 
mark, but destitute of vegetation; whilst others are overflowed with 
every returning tide 
It seems to me, that when the animalcules which form the 
corals at the bottom of the ocean, cease to live, their structures ad- 
here to each other, by virtue either of the glutinous remains within, 
or of some property in salt water ; and the interstices being gradually 
filled up with sand and broken pieces of coral washed by the sea, 
which also adhere, a mass of rock is at length formed. F uture races 
of these animalcules erect their habitations upon the rising bank, and 
die in their turn to increase, but principally to elevate, this monu- 
ment of their wonderful labours. The care taken to work perpen- 
dicularly in the early stages, would mark a surprising instinct in 
these diminutive creatures. Their wall of coral, for the most part 
in situations where the winds are constant, being arrived at the sur- 
face, affords a shelter, to leeward of which their infant colonies may 
be safely sent forth ; and to this their instinctive foresight it seems to 
be owing, that the windward side of a reef exposed to the open 
sea, is generally, if not always the highest part, and rises almost per- 
pendicular,. sometimes from the depth of 200, and perhaps many 
more fathoms. To be constantly covered with water, seems neces- 
sary to the existence of the animalcules, for they do not work, except 
ill holes upon the reef, beyond low-water mark ; but the coral sand 
and other broken remnants thrown up by the sea, adhere to the 
rock, and form a solid mass with it, as high as the common tides 
reach. That elevation surpassed, the future remnants, being rarely 
