Enough of the mere fact: the objections derived from which ought not to demand an answer among physiologists; while to those who argue physiological points in utter ignorance of all that belongs to physiology, it is probable that all answer is fruitless. It was stated before—the question is simply twofold; [p323] respiration and food. If fish can breathe indifferently salt water or fresh, for one week or one month, and if, in their new element, translated from salt to fresh, they thrive or grow, fatten and breed, the trial of three weeks or three months is a sufficient proof that they will neither sicken nor die of fresh water. If they can find food, it is indifferent whether the medium is fresh or salt. It is the misfortune of the age to understand every thing without knowing its principles; just as every man is now a physician. A few, more profound, who chance to know that salmon divide their time between fresh and salt water, possess other reasons, and find other objections; which they must be permitted to explain for themselves. I ought not, while on this particular subject, to omit one fact, which has come to my knowledge since the former papers were written, on the voluntary emigration of a fish, supposed to be peculiarly delicate and peculiarly attached to the sea, into fresh water. This is, that, in Virginia, the herring ascends the rivers, even up into the most minute communicating branches, and as far as it can reach; while a somewhat recent traveller describes them as being so abundant, that it is impossible to cross the fords on horseback during the season of their migration, without destroying them by the horse’s feet. To proceed to the _historical_ condition of this pond. I have already stated the difficulties arising from want of leisure and wealth in the proprietor, added to non-residence I should say, whence chiefly has arisen the difficulty of tracing the results. Let those try for themselves, who consider that all this might have been ascertained in a twelvemonth, and with the same means. Since the communications I formerly made, the Pilchard has been introduced. It swam away briskly, therefore it would not die of the fresh water; but it has not been retaken. The retaking of individual fish, to ascertain their presence, is a fundamental difficulty, as I before pointed out. The Brill has also been introduced since my former list. It has been retaken; and, within one year, had grown to double the original size.