—GEOGRAPHY. 10] 
. 
speech, had spread gradually across the arable English Plain until it was 
brought up sharp against the edge of the Welsh upland. That halt was 
imposed not merely by hill tribes on a defensible barrier ; but no less by 
the sudden change from agricultural to pastoral habits of life. No doubt 
there has since been some transfusion of blood across the frontier, but, 
_ apart from the original mingling of stocks as the tide of Englishry advanced 
over the plain, surprisingly little. The boundary between the races is 
quite definite to-day. You remember the heart cry of Shakespeare’s 
Mortimer : ‘ This is the deadly spite that angers me—my wife can speak 
no English, I no Welsh.’ But that was a quasi-royal marriage, and 
royal blood is a precious fluid, exceptionally mobile ! 
Thus, in the English Plain we have a typical natural region, so far 
uniform in climate and soil as to favour social continuity within, but 
-engirt by such physical features as suffice to break social continuity 
around by preventing or greatly impeding intermarriage. Within this 
natural region we have the English blood, one fluid, the same down 
through the centuries, on loan for the moment in the forty million bodies 
of the present generation. John Bull in his insularity is the exemplar 
of the myriad separate bloods and saps, each the fluid essence of a local 
variety or species of animal or plant. The climates and soils which by 
their continuities and discontinuities thus control the origin of species owe 
their power to their moisture; they, no less than the bloods and saps 
which react to them, are phenomena of the hydrosphere. 
The natural region is no mere convenient generalisation ; both by 
origin and effect it is a fundamental fact. Consider first its origin. 
‘Whether low-lying or high-lying it has a certain area or spread, and the 
: etnies reason of this is that the surface of liquid water is level. The 
technical terms of geomorphology, the concept of the morphological cycle, 
_ are based on the assumption that all landscapes are in process of grading 
down tolevel. In the case of plains, whether due to superficial denudation, 
or to marine erosion, or, again, to the deposit of sediment, the aqueous 
origin of the spread is obvious. But the boundaries which give relative 
4 ‘isolation to natural regions were not so long ago almost universally 
_ attributed, in so far as consisting of features of land relief, to the shrinkage 
_ of the earth’s size. The trend of hypothesis is now in a new direction. 
The vast accumulations of strata recorded in the foundations of the 
- mountains, and the study of isostasy by observations for gravity, point 
- to the aqueous origin of the upraising no less than of the degrading of 
4 land masses. The continents are apparently floating granitic rafts, which 
carry cargo, shifting cargo. They float on a heavier, basaltic layer which, 
_ except for certain local upwellings, comes to the surface of the lithosphere 
only in the bed of the deep ocean. The descending waters remove the 
uplands and distribute the spoil over wide lowlands and over the shallow 
sea bottom of the continental shelf. Thus, great breadths of the conti- 
-nental rafts are subjected to differential stresses—up-floating and down- 
sinking. In some cases the structure bends and there are slow readjust- 
ments of the sea level along the coasts ; elsewhere the processes of mountain 
-making—folding, faulting, shearing—are set up along certain belts which 
are axial as between the up-floating and down- -sinking areas. Whatever 
be the details of observation and speculation along these lines, it seems 
