a rampart.  View DE THOU, the historian, after his morning prayers, imploring the Divinity to purify his heart from partiality and hatred, and to open his spirit in developing the truth, amidst the contending factions of his times; and HAYDN, employed in his “Creation,” earnestly addressing the Creator ere he struck his instrument.  In moments like these, man becomes a perfect unity—­one thought and one act, abstracted from all other thoughts and all other acts.  This intensity of the mind was felt by GRAY in his loftiest excursions, and is perhaps the same power which impels the villager, when, to overcome his rivals in a contest for leaping, he retires hack some steps, collects all exertion into his mind, and clears the eventful bound.  One of our admirals in the reign of Elizabeth held as a maxim, that a height of passion, amounting to frenzy, was necessary to qualify a man for the command of a fleet; and NELSON, decorated by all his honours about him, on the day of battle, at the sight of those emblems of glory emulated himself.  This enthusiasm was necessary for his genius, and made it effective.

But this enthusiasm, prolonged as it often has been by the operation of the imaginative existence, becomes a state of perturbed feeling, and can only be distinguished from a disordered intellect by the power of volition possessed by a sound mind of withdrawing from the ideal world into the world of sense.  It is but a step which may carry us from the wanderings of fancy into the aberrations of delirium.  The endurance of attention, even in minds of the highest order, is limited by a law of nature; and when thinking is goaded on to exhaustion, confusion of ideas ensues, as straining any one of our limbs by excessive exertion produces tremor and torpor.

  With curious art the brain too finely wrought
  Preys on herself and is destroyed by Thought;
  Constant attention wears the active mind,
  Blots out her powers, and leaves a blank behind—­
  The greatest genius to this fate may bow.

Even minds less susceptible than high genius may become overpowered by their imagination.  Often, in the deep silence around us, we seek to relieve ourselves by some voluntary noise or action which may direct our attention to an exterior object, and bring us back to the world, which we had, as it were, left behind us.  The circumstance is sufficiently familiar; as well as another; that whenever we are absorbed in profound contemplation, a startling noise scatters the spirits, and painfully agitates the whole frame.  The nerves are then in a state of the utmost relaxation.  There may be an agony in thought which only deep thinkers experience.  The terrible effect of metaphysical studies on BEATTIE has been told by himself.  “Since the ‘Essay on Truth’ was printed in quarto, I have never dared to read it over.  I durst not even read the sheets to see whether there were any errors in the print, and was obliged to get a friend to do that office for me.  These studies came in time to have dreadful effects upon my nervous system; and I cannot read what I then wrote without some degree of horror, because it recalls to my mind the horrors that I have sometimes felt after passing a long evening in those severe studies.”