Mr. Townley is given somewhat to speculation in this, and a previous article, on the Decline of Fruits; and he certainly manages his subject with much ingenuity. I don't say that he is not right; but I am not yet convinced of it. Diseases, and various circumstances, affect plants, and varieties of plants. The potato is probably the best subject to illustrate his theory, but not at all conclusive. One great difficulty in arriving at the truth of the theory, is from the absence of data to govern the origin of the varieties of the plants or fruits, in question; and until he produces some reliable fact of the kind, I fancy he will be slow to find believers to the extent of his speculations. I admit this last assertion is no proof that he is wrong. Every great discoverer of a new thing, or a new principle - very different, however, from a new theory - has had the misfortune to combat prejudice, and ignorance; theories are infinitely harder than facts to surmount, unless they be fortified by illustrations conclusive and irrefragible.