ally crept over the earth's
surface little by little, year by year, just, for instance, as the
weeds of Europe are now gradually but surely creeping over the surface
of Australia."[295]

Mr. Keane is the first authority who thinks it appropriate to commence
his treatise on man with an examination of the facts which show that
"the world was peopled by migration from one centre by pleistocene
man ... who moved about like other migrating faunas, unconsciously,
everywhere following the lines of least resistance, advancing or
receding, and acting generally on blind impulse rather than of set
purpose;"[296] and it still remains with Dr. Latham to have formulated
some fixed principles of the migratory movement in his admirable
though, of course, wholly inadequate summary of man and his
migrations. I will quote the passage in full: "So long as any
continental extremities of the earth's surface remained
unoccupied--the stream (or rather the enlarging circle of migration)
not having yet reached them--the _primary_ migration is going on; and
when all have got their complement, the primary migration is over.
During this primary migration, the relations of man, thus placed in
movement and in the full, early and guiltless exercise of his high
function of subduing the earth, are in conflict with physical
obstacles and with the resistance of the lower animals only. Unless,
like Lot's wife, he turn back upon the peopled parts behind him, he
has no relations with his fellow-men--at least none arising out of the
claim of previous occupancy. In other words, during the primary
migration, the world that lay before our progenitors was either brute
or inanimate. But before many generations have passed away, all
becomes full to overflowing, so that men must enlarge their boundaries
at the expense of their fellows. The migrations that now take place
are _secondary_. They differ from the primary in many respects. They
are slower, because the resistance is that of humanity to humanity,
and they are violent, because dispossession is the object. They are
partial, abortive, followed by the fusion of different populations, or
followed by their extermination as the case may be."[297] This
passage, written so long ago as 1841, is still applicable to the facts
of modern science, and there is only to add to it that the migration
of man from a common centre, where life was easy, to all parts of the
world, where life has been difficult, must have been unde