There is a class of human beings - its name is legion - who are good and benevolent to an infinite degree, in theory. They would perform wonders if they had the power; but their vast ambition to pursue the ideal beautiful and good, cannot stoop to any of the achievements within their own contracted sphere. Their imaginative benevolence travels over boundless fields of usefulness; they endow, with unearned wealth, hospitals in the air; indulge their vanity in erecting colleges upon vast foundations of imagination; gather fruits that require no culture; rejoice over ores that are not dug from the mines; and are good and great, in their own estimation, upon this aerial principle. These men are loud in their lip-love of all that is good and great; but, because they cannot enjoy the princely advantages required to carry out their magnificent schemes, they do nothing. There are others to whom no opportunity to do good, or cultivate a grace, is lost - who would be useful to their race even in a dungeon, and would discover some beauty upon a barren rock in the ocean.

We were impressed with this truth, by becoming casually acquainted with the secret pursuits of one of our most estimable and enlightened citizens, in the fragmentary periods of leisure that fall off from a life of intense and persevering professional labor. His life has been devoted, day and night, to the studies and duties of his science; and no one would dream that Dr.--------had leisure for any thought or purpose beyond it. But who has not leisure that practises economy of time, and learns to relieve one species of labor by another of a different character, all swelling the amount of his tribute of good to the Author of all good? In the midst of a most active life, and in the centre of a crowded city, he has been for years engaged in practical experiments in horticulture, and has succeeded in attaining results that contribute more to the race than the best fought battle-field of the age. Of course, it will be supposed that he has a large space of ground for these experiments, and every aid that can further them; but, on the contrary, his garden lot is twenty by twenty feet, on the most fashionable square in Chestnut Street. Within that limited space, and in the midst of a large practice, he has still found time and means to make the most important contributions to the horticulture of the country.

By the application of science to the culture of most valuable plants, he has been enabled to add new and rich varieties; to discover and illustrate important laws, and to effect, in the offcast minutes which others fail to improve, results that will make millions more happy, when his career of graceful, modest, and untiring goodness and usefulness shall have been closed.

We dare not refer to him in such a manner that even he may discover the- allusion; and we mention the fact with the sole purpose of illustrating the truth, that there is no sphere so crowded that it has not room for a new light, a new grace, a fresh achievement for the good, a novel enjoyment for the lovers of nature. The possessors of thousands of acres might envy, and must admire, the student who, in his 'twenty by twenty lot, finds noble resources of enjoyment, and attains results which add to the comforts and happiness of his race.