But nothing in modern society has any roots.  Where to-day is some one of these great territorial houses in fifty years there may be nothing but decay.  Fashion may change from the Riviera to some other part of the Mediterranean littoral, and with fashion will go the concentration of wealth which accompanies it.

In the Middle, and especially in the latter Middle, Ages it was otherwise.  The great religious houses not only tended to accumulate wealth and to perpetuate it in the same hands (they could not gamble it away nor disperse it in luxury; they could hardly waste it by mismanagement), but they were also permanently fixed on one spot.

Such an institution as Reading, for example, or as Abingdon, went on perpetually receiving its immense revenues for generation after generation, and were under no temptation or rather had no capacity for spending it elsewhere than in the situation where their actual buildings were to be found.

In this way the great monastic houses founded a tradition of local wealth which has profoundly affected the history of the Thames Valley.  And if that valley is still to-day one of the chief districts wherein the economic power of England is concentrated, it owes that position mainly to the centuries during which the great foundations exercised their power upon the banks of the river.

The growth of great towns, one of the last phases of our national development, one which finds its example in the Thames Valley as elsewhere, and one to which we shall allude before closing these notes upon the river, has somewhat obscured the quality of this original accumulation of wealth along the Thames.  But when we come to consider the figures of the census at an earlier time, before modern commercialism and the railway had drawn wealth and population into fewer and larger centres, we shall see how considerable was the string of towns which had grown up along the stream.  And we shall especially see how fairly divided among them was the population, and, it may be presumed, the wealth and the rateable value, of the valley.

The point just mentioned in connection with the larger monastic foundations, and their artificial concentration of economic power, deserves a further elaboration, for the economic importance of a district is one of the aspects of geography which even modern analysis has dealt with very imperfectly.

Economists speak of the economic importance of such-and-such a spot because material of use to man-kind is there discovered.  Thus, people commonly point to the economic importance of the valleys all round the Pennine Range in England because they contain coal and metals, and to the economic importance of a small district in South Wales for the same reason.