454 NATURAL SCIENCE. Jone, 
colours is a mere convention—as anyone may observe who takes his 
pleasure in the Row this season. 
Geologists and others will perhaps turn first to the section of 
the book which deals with the origin of coral reefs. 
A figure which by the kindness of the publishers we have been 
able to reproduce shows how the reef forms an enormous buttress of 
rock F pressed against the sloping granite rocks G of the coast. Mr. 
Jukes, and after him the author, made most careful search for any 
evidence of upheaval, but failed to find facts against Darwin’s sub- 
sidence hypothesis. At many points along the reef enormous masses 
of storm-raised coral at first sight simulate the effects of upheaval ; 
but of exact evidence Mr. Saville Kent could find nothing to oppose 
seriously the subsidence theory. At many stations along the reef, large 
expanses of dead coral intervene between the living banks and high- 
water mark. Such banks are subjected to destructive atmospheric 
influences at every spring-tide, while living coral is above water only 
at the lowest spring-tides. Dead bivalve shells of large size such as 
Trvidacna and Pinna occupy their original positions in close contiguity 
to the dead corals; but all these results could have been caused by 
upheaval of a foot or two, and there is practically no evidence for a 
prolonged era of upheaval. 
On the other hand, all of the few big breaches in the Barrier’s 
outer rampart are opposite large estuaries. They are at present too 
remote from the estuaries (from 30 to 60 or 80 miles) for the influence 
of fresh-water to have retarded coral growth. This condition is 
by itself strong evidence for subsidence, but Mr. Saville Kent 
relies most strongly on the evidence from the geographical distribu- 
tion of animals that Australia had in former times a land-connection 
with New Guinea. It is not worth while to recapitulate the facts 
here, as all who are specially interested in the controversy will refer 
to Mr. Saville Kent’s book; but he concludes that the construction of 
the Great Barrier of Australia under conditions of subsidence, and in 
accord with the original hypothesis of Mr. Darwin, is proved. 
Towards the end of Tertiary times the great Barrier Reef existed 
as a simple fringing reef, and moderate subsidence, of the occur- 
rence of which we have abundant geological evidence, has 
turned it into its present condition. Mr. Saville Kent brings forward 
a considerable additional quantity of evidence supporting parts of the 
reef-formation theories of Murray and others. Although the Barrier 
Reef as a whole has been formed by subsidence, in the details of the 
process conditions of local growth and decay have played a large 
part. Thus, much of the actual bulk of a reef is formed of coral 
débvis—débris which comes from the breaking up under the influence 
of storms of the rapidly-growing, more fragile forms of coral. Ona 
reef at any time only a small area is actually alive, and that small 
area is turned most usually away from the mud and fresh-water on 
the landward-side, and turned towards the most abundant and freshest 

