The population works to supply its various wants; such as roads, railways, ships, houses, machinery, etc. Then follows exchange with other countries. They send us what they can best produce, and we send them what we can best and most easily produce, and so both parties gain. Thus towns spring up. Education, refinement, learning, and the higher arts follow from the active life of towns, where more brain-work is required, and the standard of life is higher. And thus we may, in imagination, follow step by step the various stages by which the highest phases of civilisation are brought to pass, beginning at the mountains and ending with human beings of the highest type,--the philosopher, artist, poet, or statesman, not omitting the gentler sex, who are often said to rule the world. The following lines of Milton possess, in the light of these facts, a deeper meaning than the poet probably intended to convey:-- "Straight mine eye hath caught new pleasures Whilst the landscape round it measures: Russet lawns and fallows grey, Where the nibbling flocks do stray; Mountains on whose barren breast The labouring clouds do often rest; Meadows trim with daisies pied, Shallow brooks and rivers wide; Flowers and battlements it sees Bosomed high in tufted trees,-- Where perhaps some beauty lies, The cynosure of neighbouring eyes." With a little rearrangement of the lines, the sequence we have indicated above would be well illustrated. The mountains must come first; then the clouds, ready to bring forth their rain; then the brooks and rivers, then "russet lawns and fallows grey,"--with their "nibbling flocks." Then come the human elements in the scene,--the "towers and battlements," containing armed warriors, well fed, no doubt, and ready to do their master's bidding; lastly, the lady who adorns the home of her lord, and, let us hope, makes it worth fighting for. For commercial purposes, large navigable rivers are of great use. And in spite of the modern railway, rivers still exert an influence in determining the routes followed by trade. London, Liverpool, Glasgow, and other busy centres of life owe their importance to the rivers which flow through them, especially since they are tidal rivers. Heavily laden barges may be seen from London Bridge going up and down with the tide every day. Since the direction as well as the existence of large rivers is regulated by mountains, it is clear that mountains have a very direct influence on the trade of the world.