Placed accidentally in a country usually considered as a focus or centre of that malaria or influence, whatever it may be, which man, correctly, perhaps, esteems as the source and cause of remittent and intermittent fevers, I have thought it might prove a labour of some utility to mankind to test the theoretical opinions to which I have alluded, by an appeal to facts submitted to more refined analyses than were known at the period of their promulgation. Time can only show in how far the views I venture to substitute for those now in vogue fairly represent the truth. A power of nature, invisible and impalpable, harasses mankind, destroys armies,[8] desolates districts and countries, slays adult man at the moment when his native land expects from him a suitable return for all the labour, trouble, and expense bestowed on him: to inquire into the nature of this poison is the object, or at least the main object, of this work. If we would rightly understand its essence and properties, it may be admitted that we ought to study carefully in the first instance its manifestations and effects; now these are tolerably well known. The most difficult part of the inquiry remains, that is, the demonstration of the essential nature of the poison or miasm giving rise to such disastrous results. All modern science leads to the conclusion that malaria, whether it originate in circumstances over which man has no control, despite every hygienic effort, or emanate from a combination of circumstances mainly caused by man himself, or be only effectual when it meets with individuals living in contempt of common sanitary precautions, must, by its material nature, be within the range of philosophical research. To Schonbein, a distinguished chemist now alive, we owe the discovery of ozone. Major Tulloch had already hinted at the doctrine that the cause of the frightful mortality in tropical countries was to be looked for in electrical conditions of the atmosphere, of whose nature we as yet are ignorant.[9] Other discoveries in this direction are sure to follow at no distant period. What so obscure a short time ago as electricity? Now look at its position, at least, as a science of application! Life, it is true, is the mystery of mysteries, equally so in its origin and extinction; yet granting this to be a truth, and foreseeing in it all the difficulties of every inquiry directed to elucidate its essential nature, every reflecting mind must be struck with the remarkable discoveries of modern times, all tending to show the close alliance between the chemical and vital phenomena, an alliance wholly unknown to the most gifted of antiquity. The modern world, right or wrong, looks to chemistry for the solution of many great and important problems, the most elevated of which unquestionably is the discovery of the causes rendering certain wide-spread localities of this earth unfit for the habitation of those at least who may not claim them as their natal