This is the fourth chapter, containing the details of the circumstances producing malaria, which have been either denied or overlooked; and it is one of the most important practical chapters in the book, inasmuch as it is to the popular ignorance of these that we must attribute a large proportion of the cases of fever occurring in common life. These, therefore, we shall mark briefly; and even the briefest notice will be of use in the way of precaution, while we must refer to the book itself for those proofs of the truth of the several views, which we could not take room to give. Generally, however, we may state this leading argument of the author, because it is brief, and, to us, appears satisfactory. It is this: that as the quantity of the poison which any person can inspire is necessarily small, and as this small quantity can be produced by a small marshy spot as well as a large one, it is the same as to the production of disease, whether the marsh is a foot square or a mile, provided the exposure be complete: while also, any piece of ground where vegetables decompose under the action of water, is virtually a marsh, or must produce malaria. This enumeration, therefore, under that view, comprises, in addition to marshes, whether fresh or salt, all the cases where water is present in such a manner as to act upon vegetables; and the chief are the following. [p104] It is shown, and by facts, that the rushy swamps of high moorlands, however small the extent, do produce this disease; and we must not here forget to name what, however, belongs to the preceding chapter, woods and coppices, little suspected in England, yet shown to be the cause of fevers in Wales, and also in Sussex; very probably, every where else. It is also shown that meadows and moist pastures, whether in flat lands or on elevations, generate fevers; and very particularly, should they have been affected by inundation or unusual moisture, and if that should be followed by heat. And while it is also specifically shown how, in all cases, it is the produce of the drains or ditches required in meadow lands, it is distinctly proved that, even without these, malaria is produced, or that it is generated by the meadow or moist pasture itself.