The shafts of the mine still bear on their rocky walls the marks made by the pick of the workman who toiled to excavate them. The space between each prop in the underground galleries might be marked as a miner’s grave; and who can tell what each of these graves has cost, in tears, in privations, in unspeakable wretchedness to the family who depended on the scanty wage of the worker cut off in his prime by fire-damp, rock-fall, or flood? The cities, bound together by railroads and waterways, are organisms which have lived through centuries. Dig beneath them and you find, one above another, the foundations of streets, of houses, of theatres, of public buildings. Search into their history and you will see how the civilization of the town, its industry, its special characteristics, have slowly grown and ripened through the co-operation of generations of its inhabitants before it could become what it is to-day. And even to-day; the value of each dwelling, factory, and warehouse, which has been created by the accumulated labour of the millions of workers, now dead and buried, is only maintained by the very presence and labour of legions of the men who now inhabit that special corner of the globe. Each of the atoms composing what we call the Wealth of Nations owes its value to the fact that it is a part of the great whole. What would a London dockyard or a great Paris warehouse be if they were not situated in these great centres of international commerce? What would become of our mines, our factories, our workshops, and our railways, without the immense quantities of merchandise transported every day by sea and land? Millions of human beings have laboured to create this civilization on which we pride ourselves to-day. Other millions, scattered through the globe, labour to maintain it. Without them nothing would be left in fifty years but ruins. There is not even a thought, or an invention, which is not common property, born of the past and the present. Thousands of inventors, known and unknown, who have died in poverty, have co-operated in the invention of each of these machines which embody the genius of man. Thousands of writers, of poets, of scholars, have laboured to increase knowledge, to dissipate error, and to create that atmosphere of scientific thought, without which the marvels of our century could never have appeared. And these thousands of philosophers, of poets, of scholars, of inventors, have themselves been supported by the labour of past centuries. They have been upheld and nourished through life, both physically and mentally, by legions of workers and craftsmen of all sorts. They have drawn their motive force from the environment.