The northern and southern banks incline sufficiently towards the stream in the centre to allow of proper drainage. The stream itself furnished water in sufficient volume to provide for the wants of ten thousand men, if it had been turned from its channel above the stockade, and introduced into the prison by simple sluices. But to this important item there was not the least attention paid. To preface the analysis of this stockade, &c., we may wisely review the remarks of the late Dr. Jackson, the chief medical officer of the British army. V. "A necessity occurs in war, on many occasions, which leaves no option of choice in occupying posts of an unhealthy character: but there is, unfortunately, an authority, derived from example and the sanction of great names, which directs the military officer, when under no military necessity, to fix his encampment on grounds which are unhealthy in themselves, or which are exposed by position to the influence of noxious causes, which are carried from a distance. "Such advice proceeds from the desire to act on a presumption of knowledge, which cannot be ascertained, rather than to act by the experience of facts, which man is qualified to observe and verify. "It is consonant with the experience of military people, in all ages and in all countries, that camp diseases most abound near the muddy banks of large rivers, near swamps, and ponds, and on grounds which have been recently stripped of their woods. The fact is precise: but it has been set aside to make way for an opinion. "It was assumed, about half a century since, by a celebrated army physician, that camp diseases originate from causes of putrefaction, and that putrefaction is connected radically with a stagnant condition of the air. As streams of air usually proceed along rivers, with more certainty and force than in other places, and as there is evidently a more certain movement of air, that is, more winds, on open grounds than among woods and thickets, this sole consideration, without any regard to experience, influenced opinion, and gave currency to the destructive maxim, that the banks of rivers, open grounds, and exposed heights, are the most eligible situations for the encampment of troops. They are the best ventilated: they must, if the theory be true, be the most healthy. The fact is the reverse. But demonstrative as the fact may be, fashion has more influence than multiplied examples of fact, experimentally proved. "Encampments are still formed in the vicinity of swamps, or on grounds which are newly cleared of their woods, in obedience to theory, and contrary to fact. The savage, who acts by instinct, or who acts directly from the impressions of experience, has in this instance the advantage over the philosopher, who, reasoning concerning causes he cannot know, and acting according to the result of his reasonings, errs and leads others astray by the authority of his name.