SECTION C. 
GEOLOGY AND iow ee 
PRESIDENTIAL ADDRESS. 
By T..S. Haut, M.A., University, Melbourne. 
THE POSSIBILITY OF DETAILED CORRELATION 
OF AUSTRALIAN FORMATIONS WITH THOSE 
OF THE NORTHERN HEMISPHERE. 
“Tt is the aim of the Stratigraphical Geologist,” says a 
well-known author (Marr. 1898, p. 1), ‘‘ to record the events 
which have occurred during the existence of the earth in 
the order in which they have taken place.’ In the case’ 
of formations which come into contact, the order of succes- 
sion can be sectled by the Law of Superposition—the under- 
lying strata are the older. But the law is not al vays 
applicable, and the identification of strata by their fossil 
contents becomes necessary, and thus cheir relationship to 
other sets of strata is made possible. As a matter of fact, 
no two serie» of beds, separated from one another by any 
reasonable distance. ever do contain exactly identicai faunas. . 
but differences. more or less marked, are discernible on care- 
ful examination. These differences may be due to several 
causes, such as slight differences in age. geographical re 
‘moteness, or different conditions of deposition as regards 
depth of the water, the rate of sedimentation, and the 
numerous other factors which cause differences in the fauna 
at various places near our shores to-day. 
In recent times geographical remoteness is an important 
factor in bringing about differences in the facies of faumas. 
As distances increase, specific and generic agreements de 
crease. and, speaking generally. the wider spread is any 
form the older is it geologicaily. The converse, however. is 
not always true. for many genera or species new restricted 
to small and isolated areas have a considerable geological 
antiquity. Highly specialised types, as opposed to highly 
organised ones, are prone to have but a short geological 
range. and vat these forms. as, for instance, those terminal 
twigs of a gs enealogical tree, which bud forth into spines and 
bizarre ornament, are just those which are eas€® to recognise 
