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." GOLDONI, after a rash exertion of writing sixteen plays in a year, confesses he paid the penalty of the folly. He flew to Genoa, leading a life of delicious vacuity. To pass the day without doing anything, was all the enjoyment he was now capable of feeling. But long after he said, "I felt at that time, and have ever since continued to feel, the consequence of that exhaustion of spirits I sustained in composing my sixteen comedies." The enthusiasm of study was experienced by POPE in his self-education, and once it clouded over his fine intellect. It was the severity of his application which distorted his body; and he then partook of a calamity incidental to the family of genius, for he sunk into that state of exhaustion which SMOLLETT experienced during half a year, called a _coma vigil,_ an affection of the brain, where the principle of life is so reduced, that all external objects appear to be passing in a dream. BOERHAAVE has related of himself, that having imprudently indulged in intense thought on a particular subject, he did not close his eyes for six weeks after; and TISSOT, in his work on the health of men of letters, abounds in similar cases, where a complete stupor has affected the unhappy student for a period of six months.