To read these volumes is like going out ourselves into the forest with an expert guide who sees everything and who has at his command an unlimited store of anecdote and chatty reminiscence of birds and animals and even plants. To Burroughs, Nature was sufficient in herself. He loved her for the feelings she could arouse within him, for the recollections she could stir of the springtime of his life, for the beauty and the harmony that everywhere he found, and for the elemental laws that he saw on all sides at work and that stirred his curiosity. He had no desire to study Nature to secure evidences of a governing personality. He would draw no moral and offer no solutions of the problem of good and evil. Of the fortunes of the spirit of man he cared but little; as for himself, serene, he would fold his hands and wait. He was no mystic like Thoreau, listening for higher harmonies and peering eagerly beyond every headland to discover perchance the sources of the Nile. Upon him there was no necessity save to observe, to record, to discover new phenomena, to enlarge the store of facts, to walk flat-footed upon the material earth and observe the working of the physical mechanics about him and to teach others to observe them and to enjoy them. To appreciate the difference between Burroughs and Thoreau one has but to read them side by side. For instance, on March 21, 1853, Thoreau makes this entry: As I was rising this crowning road, just beyond the old lime kiln, there leaked into my open ear the first peep of a hyla from some far pool ... a note or two which scarcely rends the air, does no violence to the zephyr, but yet leaks through all obstacles and far over the downs to the ear of the listening naturalist, as it were the first faint cry of the new-born year, notwithstanding the notes of birds. Where so long I have heard the prattling and moaning of the wind, what means this tenser, far-piercing sound? Burroughs writes of the same subject in this way: From what fact or event shall we really date the beginning of spring? The little piping frogs usually furnish a good starting point. One spring I heard the first note on the 6th of April; the next on the 27th of February; but in reality the latter season was only about two weeks earlier than the former.... The little piper will sometimes climb a bullrush to which he clings like a sailor to a mast, and send forth his shrill call. There is a Southern species, heard when you have reached the Potomac, whose note is far more harsh and crackling. To stand on the verge of a swamp vocal with these, pains and stuns the ear. Then in a foot-note: The Southern species is called the green hyla. I have since heard them in my neighborhood on the Hudson.