A further consideration has admitted that not only places where things useful to mankind are discovered, but places naturally fitted for their exchange have an economic importance peculiarly their own.  Indeed, the more history is studied from the point of view of economics, the more does this kind of natural opportunity emerge, and the less does the political importance of purely productive areas appear.  The mountain districts of Spain, the Cornish peninsula, were centres of metallic industry of the first importance to the Romans, but they remained poor throughout the period of Roman civilisation.  To-day the farmer in the west of America, the miner and the clerk in Johannesburg, are perhaps more numerous, but as a political force no wealthier for the opportunities of their sites:  the economic power which they ultimately produce is first concentrated in the centres of exchange where the wealth they produce is handled.

Now there is a third basis for the economic importance of a district, and as this third basis is indefinitely more important than the other two, it has naturally been overlooked in the analysis of the universities.  This basis is the basis of residence.  Given that a conqueror, or a seat of Government established by routine, is established in a particular place and chooses there to remain; or given that the pleasure attached to a particular site—­its natural pleasures or the inherited grandeur of its buildings or what not—­make it an established residence for those who control the expenditure of wealth, then that place will acquire an economic importance which has for its foundation nothing more material than the human will.  Thither wealth, wherever produced, will flow, and there will be discovered that ultimate motive force of all production and of all exchange, the effective demand of those possessors who alone can set the industrial machine in motion.

This has been abundantly true in every period of the world’s history, whenever commerce existed upon a considerable scale, or whenever a military force sufficiently universal was at the command of wealthy men.

It is particularly true to-day.  To-day not the natural centres of exchange, still less the natural centres of production, determine what places in the world shall be wealthy and what shall not.  The surplus of the wealth produced by the Egyptian fellaheen is carefully collected by English officials and largely consumed in Paris; the wealth produced by the manufacturers of North England is largely spent in the south of England and upon the Continent; until their recent and successful revolt, the wealth produced by the Irish peasantry was largely spent in London and upon the Riviera.

The economic importance, then, of the Thames Valley has not diminished, but increased since South England ceased to be the main field of production.