PRESIDENTIAL ADDRESS.—SECTION C. 
(Geology and Mineralogy). 
A REFUTATION OF THE DOCTRINE OF HOMOTAXY. 
By PROFESSOR RALPH TATE, F.G.S., ADELAIDE, 
SOUTH AUSTRALIA. 
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Ir had been considered up to a certain date that identity of fossil 
contents was proof of equal time-deposition of the sediments 
yielding the identical fossils. This fundamental law of strati- 
graphical geology was established by William Smith at the 
beginning of this century, and has been universally accepted as 
applicable to self-contained areas; but as applied to countries 
separated by wide oceanic basins, it was challenged by the late 
Professor T. H. Huxley in an anniversary address to the Geo- 
logical Society, London, 1862, and the main conclusions set forth 
by him may be shortly expressed by the phrase that ¢dentity of 
fossil contents is not a proof of contemporaneity. This is a 
definition of the word homotazis in its geological application ; 
the word in itself means only equal order, and it may be re- 
marked that the order and life in two widely separated areas 
may be equal or the same, but on the doctrine of homotaxis the 
deposits are not equal in time. 
The doctrine of homotaxis has held a prominent place in our 
geological literature since its promulgation ; however, Professor 
Sollas has this year questioned its validity, so I gather from 
“ Nature,’ 19th October, in its summary of geology at the 
British Association Adv. Science, which reports as follows :— 
“He discussed homotaxy and contemporaneity, showing that 
Huxley’s well-known contention could not be sustained, and had 
led to much misunderstanding of the value of fossil evidence.” 
As the above quotation is the only information I have at the time 
of writing this essay (November, 1899), it will be conceded that 
what concordances may eventually be found between his views 
and mine, they have been arrived at independently. I may say 
in this connection that this leading question of homotaxy has 
been adversely pressed to my notice by the increasing growth of 
an accurate knowledge of Australian paleontology, and has been 
a subject of lectures to my classes for many years past. I may 
