but these positions are nearly always central to limited areas over which travel is uninterrupted. The great market of Nijni Novgorod in Russia is an example of this sort. Chicago in the United States of America is another. But London is no parallel to such cases as these, so far as the world or even Europe is concerned. It is fairly central (as we shall see) to what was once the chief wealth of England: it is ex-centric to all else. [Illustration: THE THAMES FROM GREENWICH PARK] Still less will the many arguments based upon fairly modern conditions solve the problem which confronts us. Thus the great export trade of modern England is mainly based upon coal. But the estuary of the Thames is not a natural place of export for coal. The political relations which necessarily bind this country to-day to other countries of the same speech throughout the New World have a vast effect in continuing and expanding our oversea exchanges, but all the ports natural to such ties lie upon our south or west. London does not face the New World. It looks away from it. The truth is that the singular position of the Lower Thames as a terminal for international commerce, and of its port as an international market, must be sought in a medley of causes, the chief of which fall into two clear categories. We have first the causes which made London what it was before the transformation of commerce through the discoveries of the Renaissance and the later gigantic expansion which reposes upon modern facilities of communication. Once London is thus established as the second great city of the West, we have the later causes which permit it to continue in the enjoyment of that position, and to nourish it until the city whose port was the Thames became not the second but by far the first of all the great markets in wealth, population, and shipping. I will take these two sets of causes separately. As to the first, what made the greatness of the Thames as a port for London, and of London, therefore, as a market before the modern era of geographical discovery? A natural market exists only where two natural conditions are present: ease of approach from without, and what may be called _draining power_ from within. I mean by ease of approach from without a natural facility for the arrival of goods from areas of production foreign to those of the market. And I mean by “draining power from within” some topographical or other condition which makes domestic produce run naturally towards the one centre of this market. To these two natural conditions must be added two further political ones: first, one must have such a society connected with that market as gives it security, and, secondly, such a society as is organised by its activity and adventure for production or for exchange, or for both.