A Book upon Farm Drainage! What can a person find on such a subject to write a book about? A friend suggests, that in order to treat any one subject fully, it is necessary to know everything and speak of everything, because all knowledge is in some measure connected. With an earnest endeavor to clip the wings of imagination, and to keep not only on the earth, but to burrow, like a mole or a sub-soiler, _in_ it, with a painful apprehension lest some technical term in Chemistry or Philosophy should falsely indicate that we make pretensions to the character of a scientific farmer, or some old phrase of law-Latin should betray that we know something besides agriculture, and so, are not worthy of the confidence of practical men, we have, nevertheless, by some means, got together more than a bookfull of matter upon our subject. Our publisher says our book must be so large, and no larger--and we all know that an author is but as a grasshopper in the hands of his publisher, and ought to be very thankful to be allowed to publish his book at all. So we have only to say, that if there is any chapter in this book not sufficiently elaborate, or any subject akin to that of drainage, that ought to have been embraced in our plan and is not, it is because we have not space for further expansion. The reader has our heartfelt sympathy, if it should happen that the very topic which most interests him, is entirely omitted, or imperfectly treated; and we can only advise him to write a book himself, by way of showing proper resentment, and put into it everything that everybody desires most to know. A book that shall contain all that we do _not_ know on the subject of drainage, would be a valuable acquisition to agricultural literature, and we bespeak an early copy of it when published. IRRIGATION is a subject closely connected with drainage, and, although it would require a volume of equal size with this to lay it properly before the American public, who know so little of water-meadows and liquid-manuring, and even of the artificial application of water to land in any way, we feel called upon for an apology for its omission. Lieutenant Maury, whose name does honor to his nation over all the civilized world, and on whom the blessings of every navigator upon the great waters, are constantly showered, in a letter which we had the honor recently to receive from him, thus speaks of this subject: