One characteristic April feature, and one that delights me very much, is the perfect emerald of the spring runs while the fields are yet brown and sere,--strips and patches of the most vivid velvet green on the slopes and in the valleys. How the eye grazes there, and is filled and refreshed! I had forgotten what a marked feature this was until I recently rode in an open wagon for three days through a mountainous, pastoral country, remarkable for its fine springs. Those delicious green patches are yet in my eye. The fountains flowed with May. Where no springs occurred, there were hints and suggestions of springs about the fields and by the roadside in the freshened grass,--sometimes overflowing a space in the form of an actual fountain. The water did not quite get to the surface in such places, but sent its influence. The fields of wheat and rye, too, how they stand out of the April landscape,--great green squares on a field of brown or gray! Among April sounds there is none more welcome or suggestive to me than the voice of the little frogs piping in the marshes. No bird-note can surpass it as a spring token; and as it is not mentioned, to my knowledge, by the poets and writers of other lands, I am ready to believe it is characteristic of our season alone. You may be sure April has really come when this little amphibian creeps out of the mud and inflates its throat. We talk of the bird inflating its throat, but you should see this tiny minstrel inflate _its_ throat, which becomes like a large bubble, and suggests a drummer-boy with his drum slung very high. In this drum, or by the aid of it, the sound is produced. Generally the note is very feeble at first, as if the frost was not yet all out of the creature's throat, and only one voice will be heard, some prophet bolder than all the rest, or upon whom the quickening ray of spring has first fallen. And it often happens that he is stoned for his pains by the yet unpacified element, and is compelled literally to "shut up" beneath a fall of snow or a heavy frost. Soon, however, he lifts up his voice again with more confidence, and is joined by others and still others, till in due time, say toward the last of the month, there is a shrill musical uproar, as the sun is setting, in every marsh and bog in the land. It is a plaintive sound, and I have heard people from the city speak of it as lonesome and depressing, but to the lover of the country it is a pure spring melody. The little piper will sometimes climb a bulrush, 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. The call of the Northern species is far more tender and musical. [Footnote: The Southern species is called the green hyla. I have since heard them in my neighborhood on the Hudson.]