All we know about the private and essential natural history of the bees, the birds, the fishes, the animals, the plants, is the result of close, patient, quick-witted observation. Yet Nature will often elude one for all his pains and alertness. Thoreau, as revealed in his journal, was for years trying to settle in his own mind what was the first thing that stirred in spring, after the severe New England winter,--in what was the first sign or pulse of returning life manifest; and he never seems to have been quite sure. He could not get his salt on the tail of this bird. He dug into the swamps, he peered into the water, he felt with benumbed hands for the radical leaves of the plants under the snow; he inspected the buds on the willows, the catkins on the alders; he went out before daylight of a March morning and remained out after dark; he watched the lichens and mosses on the rocks; he listened for the birds; he was on the alert for the first frog ("Can you be absolutely sure," he says, "that you have heard the first frog that croaked in the township?"); he stuck a pin here and he stuck a pin there, and there, and still he could not satisfy himself. Nor can any one. Life appears to start in several things simultaneously. Of a warm thawy day in February the snow is suddenly covered with myriads of snow fleas looking like black, new powder just spilled there. Or you may see a winged insect in the air. On the selfsame day the grass in the spring run and the catkins on the alders will have started a little; and if you look sharply, while passing along some sheltered nook or grassy slope where the sunshine lies warm on the bare ground, you will probably see a grasshopper or two. The grass hatches out under the snow, and why should not the grasshopper? At any rate, a few such hardy specimens may be found in the latter part of our milder winters wherever the sun has uncovered a sheltered bit of grass for a few days, even after a night of ten or twelve degrees of frost. Take them in the shade, and let them freeze stiff as pokers, and when thawed out again they will hop briskly. And yet, if a poet were to put grasshoppers in his winter poem, we should require pretty full specifications of him, or else fur to clothe them with. Nature will not be cornered, yet she does many things in a corner and surreptitiously. She is all things to all men; she has whole truths, half truths, and quarter truths, if not still smaller fractions. The careful observer finds this out sooner or later. Old fox-hunters will tell you, on the evidence of their own eyes, that there is a black fox and a silver-gray fox, two species, but there are not; the black fox is black when coming toward you or running from you, and silver gray at point-blank view, when the eye penetrates the fur; each separate hair is gray the first half and black the last. This is a sample of nature's half truths.