It is probable that mere increase of vitality in itself is sufficient to account for this new delicacy of the physical senses.  The senses adapt themselves to their environment.  An example of this is found in the absence of what is called long sight among city children.  Having no extensive horizon constantly before the eye, the power of discerning distant objects gradually decays.  On the contrary a child brought up upon the African veldt, where he is daily confronted with almost infinite distances, acquires what seems to be an almost preternatural sharpness of vision.  It is the same with hearing.  The savage can distinguish sounds which are entirely inaudible to the civilised man.  The footfall of his enemy, the beat of a horse’s hoofs, the movement of a lion in the jungle, are heard at what appear impossible distances.  I do not seek to offer any absolute explanation of these phenomena as regards myself, but I state the fact that in returning to a natural life I found a remarkable quickening of my physical senses.  As my eye became accustomed to the wide moorland prospects I found myself increasingly able to discriminate distant objects.  Flowers that had seemed to me to smell pretty much alike, now had distinct fragrances.  I knew when I woke in the morning from which direction the wind came, by its odour; the wind from the moorland brought the scent of heather and wild thyme, the wind from the glen the scent of water.

It was the same with sound.  Properly speaking there is no such thing as silence in Nature.  The silence, or what seems silence, is divisible into a multitude of minute sounds.  Everything in Nature is toiling and straining at its task, the sap in the tree, the rock balanced on its bed of clay, the grass-blade pushing and urging its way toward the sun.  And as there is no real silence, so there is no real solitude in a world where every atom is vigorously at work.  Wordsworth’s conception of Nature as a Presence becomes at once intelligible when we live close to the heart of Nature.  Had Wordsworth lived in towns his poetry could never have been written, nor can its central conception of Nature as a Presence be understood by the townsman.  I had often enough read the wonderful lines—­

        And I have felt
  A presence that disturbs me with the joy
  Of elevated thoughts:  a sense sublime
  Of something far more deeply interfused,
  Whose dwelling is the light of setting suns,
  And the round ocean, and the living air,
  And the blue sky, and in the mind of man
  A motion and a spirit, that impels
  All thinking things, all objects of all thought,
  And rolls through all things.