In some respects he let himself be.  His exterior oddities never seem to have toned down much; he could not be taught to introduce tidiness or method into his office; nor did he make himself an exact lawyer; a rough and ready familiarity with practice and a firm grasp of larger principles of law contented him without any great apparatus of learning.  His method of study was as odd as anything else about him; he could read hard and commit things to memory in the midst of bustle and noise; on the other hand, since reading aloud was his chosen way of impressing what he read on his own mind, he would do it at all sorts of times to the sore distraction of his partner.  When his studies are spoken of, observation and thought on some plan concealed in his own mind must be taken to have formed the largest element in these studies.  There was, however, one methodic discipline, highly commended of old but seldom perhaps seriously pursued with the like object by men of forty, even self-taught men, which he did pursue.  Some time during these years he mastered the first six Books of Euclid.  It would probably be no mere fancy if we were to trace certain definite effects of this discipline upon his mind and character.  The faculty which he had before shown of reducing his thought on any subject to the simplest and plainest terms possible, now grew so strong that few men can be compared with him in this.  He was gaining, too, from some source, what the ancient geometers would themselves have claimed as partly the product of their study:  the plain fact and its plain consequences were not only clear in calm hours of thought, but remained present to him, felt and instinctive, through seasons of confusion, passion, and dismay.  His life in one sense was very full of companionship, but it is probable that in his real intellectual interests he was lonely.  To Herndon, intelligently interested in many things, his master’s mind, much as he held it in awe, seemed chillingly unpoetic—­which is a curious view of a mind steeped in Shakespeare and Burns.  The two partners had been separately to Niagara.  Herndon was anxious to know what had been Lincoln’s chief impression, and was pained by the reply, “I wondered where all that water came from,” which he felt showed materialism and insensibility.  Lincoln’s thought had, very obviously, a sort of poetry of its own, but of a vast and rather awful kind.  He had occasionally written verses of his own a little before this time; sad verses about a friend who had become a lunatic, wondering that he should be allowed to outlive his mind while happy young lives passed away, and sad verses about a visit to old familiar fields in Indiana, where he wandered brooding, as he says,

  “Till every sound appears a knell,
  And every spot a grave.”

They are not great poetry; but they show a correct ear for verse, and they are not the verses of a man to whom any of the familiar forms of poetic association were unusual.  They are those of a man in whom the habitual undercurrent of thought was melancholy.