Besides this partially new theory of the causes of glacial epochs, the
work contained a fuller statement of the various kinds of evidence
proving that the great oceanic basins are permanent features of the
earth's surface, than had before been given; also a discussion of the
mode of estimating the duration of geological periods, and some
considerations leading to the conclusion that organic change is now less
rapid than the average, and therefore that less time is required for
this change than has hitherto been thought necessary. I was also, I
believe, the first to point out the great difference between the more
ancient continental islands and those of more recent origin, with the
interesting conclusions as to geographical changes afforded by both;
while the most important novelty is the theory by which I explained the
occurrence of northern groups of plants in all parts of the southern
hemisphere--a phenomenon which Sir Joseph Hooker had pointed out, but
had then no means of explaining.[7]

In 1878 Wallace wrote a volume on Australasia for Stanford's "Compendium
of Geography and Travel." A later edition was published in 1893, which
contained in addition to the physical geography, natural history, and
geology of Australia, a much fuller account of the natives of Australia,
showing that they are really a primitive type of the great Caucasian
family of mankind, and are by no means so low in intellect as had been
usually believed. This view has since been widely accepted.

Having, towards the close of 1885, received an invitation from the
Lowell Institute, Boston, U.S.A., to deliver a course of lectures in the
autumn and winter of 1886, Wallace decided upon a series which would
embody those theories of evolution with which he was most familiar, with
a special one on "The Darwinian Theory" illustrated by a set of original