Geographical concentration and regional integration of industry are in general accompanied or followed by concentration in the units of production. But it must be emphasized from the beginning that this need not necessarily be the case. It will be recalled from what has been explained in a historical paragraph, that in the sixteenth to the eighteenth centuries the widening of markets, and the geographical concentration of production in certain districts well adapted to the supply of far distant markets, did not at once result in a wholesale revolution of industrial units, but merely led to a collective organization of their sales by industrial capitalists and to the putting-out system. Again, while during a large part of the nineteenth century English coal-mining enjoyed a monopolist domination on most foreign markets, 1 British collieries could by no means be considered as being “concentrated”. And to give another example: in the German potash industry, which in the first thirty years of its existence might be taken as a classic example of geographical integration, the very reverse of a concentration of units was taking place; the increase of undertakings and pits was so much accelerated that in 1913 the number of undertakings had risen to 167 and in 1916 to 207.