her fleets, crippled her power, annihilated her army, as at Walcheren, and broken up the health of many a sturdy yeoman by the banks of the Scheldt, of the Thames and its tributaries. To this poison the term malaria has been applied--a word borrowed from the Italian. This malaria is presumed, whatever it may be, to be the cause (though not exclusively), on evidence almost amounting to a certainty, of the fevers marked by intermissions and remissions; it may also be the cause of the more terrible febrile diseases called the yellow fever, the black vomit, &c., of tropical countries. On this I do not insist. As regards intermitting and remitting febrile affections, we are all but certain that to such localities as I have just alluded to, their origin may be traced, however they may originate elsewhere. A long residence in Holland and Belgium (countries supposed by many to be in an especial manner the hot-bed and active parent of malaria) has enabled me to observe, I trust in an unprejudiced manner, some facts which may have escaped the observation of others. Long resident in that land, on which perished miserably the best equipped army (an army composed of veterans) which ever, perhaps, quitted England for foreign aggression; in that land on which perished the chosen garrisons of the mighty Napoleon; on that spot where they dragged on a miserable existence, or perished in the prime of life; the writer of this essay enjoyed the best of health. Even admitting the full influence of a vigorous constitution, and an innate vitality equal to the neutralization of all malaria, a something must still be ascribed to observation leading him to avoid the hurtful and insalubrious agencies at work around him--agencies ever active, ever seeking to destroy. This information the author has thought might be useful to others, and with this view he submits it to the public.[2] [2] Medical authors of the highest repute are exceedingly vague in their ideas respecting the nature of malaria; nor will it ever be otherwise until the question be taken up by the strictly scientific. Thus, Sir John Forbes says, in his “Holiday:”--“As the unknown thing which we term malaria or miasma of marshes, under certain circumstances gives rise at one time to simple ague, at another to a fatal remittent fever, &c.; and produces at times a morbid enlargement of the spleen, at others diseases of the liver, &c.; so I can imagine that some other _malaria_, or unknown thing or influence of local origin, may be the cause of ordinary bronchocele, of goitre of the Alps, and also of cretinism.” From the 1st of August to December the author hunted and waded through the marshes of Belgium and Holland in quest of water-fowl; his impunity from fever may be in part ascribed to a hardy training in early life. CHAPTER I. MALARIA--ITS SUPPOSED ORIGIN.