"These fens were drained and enclosed pursuant to an Act of Parliament, which was obtained for that purpose in the year 1766. Three principal drains were then cut, fourteen feet wide, and about four miles long, into which the water was conducted from every part of the Carr southward, to the little river Torne, at Rossington Bridge, whence it flows into the Trent. Before these drainings, the ground was liable to frequent inundations; and about the centre there was a decoy for wild ducks; there is still a deep water there of considerable extent, in which very large pike and eels are found. The soil, which was so boggy at first that horses were lost in attempting to drink at the drains, has been brought {178} into good cultivation, (as all such ground may be) to the great improvement of the district; for till this improvement was effected, _intermittent fevers and sore throats were prevalent there, and they have ceased from the time the land was drained_. The most unhealthy season now, is the spring, when cold winds, from the north and north-east, usually prevail during some six weeks; at other times Doncaster is considered to be a healthy place. It has been observed that when endemic(?) diseases arrive there, they uniformly come from the south; and that the state of the weather may be foretold from a knowledge of what it has been at a given time in London, making an allowance of about three days, for the chance of winds. Here, as in all places which lie upon a great and frequented road, the transmission of disease has been greatly facilitated by the increase of travelling." I feel certain of being excused for transcribing this long passage from Southey. It would have been impossible to convey its whole meaning without giving it entire. The continuation of the chapter is no less instructive and applicable to our subject, though more particularly so to an extension of the enquiry. The sore throats and intermittents, from which Doncaster has been freed, by the drainage of Potteric Carr, informs us at once that decomposing matter is the material by which the poison of fever is vivified and sustained, the wet and boggy state of the soil is just the condition, when no drainage exists, to bring into activity the germs of {179} disease, which otherwise would lie latent. So satisfied and acquainted are we with the elements necessary for the production of fever, that we might as certainly bring about an endemic intermittent by forming an artificial bog, as we could be sure of growing mushrooms by making a bed in the manner laid down by gardeners for this purpose. Dr. Lindley also says, "the _Polyporus fomentarius_ has been artificially produced in Germany, but merely by placing wood in a favourable situation, and keeping it well moistened. Five or six crops were obtained in the year."