To those doing outpost-duty on an island, however large, the main-land has all the fascination of forbidden fruit, and on a scale bounded only by the horizon.  Emerson says that every house looks ideal until we enter it,—­and it is certainly so, if it be just the other side of the hostile lines.  Every grove in that blue distance appears enchanted ground, and yonder loitering gray-back, leading his horse to water in the farthest distance, makes one thrill with a desire to hail him, to shoot at him, to capture him, to do anything to bridge this inexorable dumb space that lies between.  A boyish feeling, no doubt, and one that time diminishes, without effacing; yet it is a feeling which lies at the bottom of many rash actions in war, and of some brilliant ones.  For one, I could never quite outgrow it, though restricted by duty from doing many foolish things in consequence, and also restrained by reverence for certain confidential advisers whom I had always at hand, and who considered it their mission to keep me always on short rations of personal adventure.  Indeed, most of that sort of entertainment in the army devolves upon scouts detailed for the purpose, volunteer aides-de-camp and newspaper-reporters,—­other officers being expected to be about business more prosaic.

All the excitements of war are quadrupled by darkness; and as I rode along our outer lines at night, and watched the glimmering flames which at regular intervals starred the opposite river-shore, the longing was irresistible to cross the barrier of dusk, and see whether it were men or ghosts who hovered round those dying embers.  I had yielded to these impulses in boat-adventures by night,—­for it was a part of my instructions to obtain all possible information about the Rebel outposts,—­and fascinating indeed it was to glide along, noiselessly paddling, with a dusky guide, through the endless intricacies of those Southern marshes, scaring the reed-birds, which wailed and fled away into the darkness, and penetrating several miles into the interior, between hostile fires, where discovery might be death.  Yet there were drawbacks as to these enterprises, since it is not easy for a boat to cross still water, even on the darkest night, without being seen by watchful eyes; and, moreover, the extremes of high and low tide transform so completely the whole condition of those rivers that it needs very nice calculation to do one’s work at precisely the right time.  To vary the experiment, I had often thought of trying a personal reconnaissance by swimming, at a certain point, whenever circumstances should make it an object.