There are many persons in the world to whom it is no uncommon occurrence, to rise from their bed in the morning more wearied and exhausted, both in mind and body, than when they retired to it the evening before: to whom sleep is frequently an object of terror rather than comfort, and who seek in vain for relief from the means usually recommended by Physicians. To such persons I dedicate this little work; for their information I have laid down, in as clear terms as the subject will admit, the history of those diseases, which, by depriving us of the benefit of sleep, and driving rest from our couch, often render life itself miserable, and lay the foundation of formidable, and sometimes of fatal diseases. Amongst those affections which thus break in upon our repose, the most formidable and the most frequent is the disease called Night-Mare; the history of which, with its various modifications, I have endeavoured to give with as much accuracy as possible, and have attempted also to investigate its nature and immediate causes, as well as to point out the best mode of obtaining relief. Very little assistance could be obtained in this undertaking, from the writings of modern Physicians, who have paid little or no attention to it: those of the sixteenth and seventeenth centuries, seem to have well understood both its causes and cure, but differed much amongst themselves respecting its nature, as will ever be the case when we attempt to reason on any subject which is above our comprehension. I have availed myself of all the light which these illustrious men could throw upon the subject, which is not a little; but my principal information respecting it has arisen from a personal acquaintance with the disease itself, for a long series of years, having been a victim to it from my earliest infancy. I have never met with any person who has suffered to so great an extent from this affection, or to whom it was become so habitual. To eradicate thoroughly a disease so deeply rooted and of so long duration, cannot be expected: but I have so far succeeded as to bring it under great control, and to keep myself free from its attacks for several months together; or indeed scarcely ever to be disturbed by it at all, but when I have deviated from those rules which experience has proved to be sufficient to secure me from all danger of it.