Were it not for the operation of unfavourable circumstances of the nature specified, a body in health, were no special interposition of the Almighty hand made, would go on in the healthy performance of its functions, till the frailty and decay, incident to old age, would overtake it. In general those diseases which are observed to prevail to a great extent, and over a large tract of country at the same time, are so uniformly coincident with circumstances of an unwholesome tendency, connected with those agencies above referred to, that they appear at once to the candid and unprejudiced inquirer, to stand in the relation of cause and effect. Surely it should cause no difficulty, nor occasion any necessity for the calling in a principle, atmospheric contagion, without any other evidence, that those effects are occasionally found not confined to one spot merely, but are seen developed in an extended sphere—for, assuredly, it can require no extraordinary effort of the mind to conceive that the agent acting and causing disease in one place, or individual case, may with equal force, and with a like result, act in many situations, and in respect to many persons. The presence of certain operations in several situations by no means proves that they have reproduced themselves. Day-light is manifest in many countries, within certain latitudes at the same hour, but it has never been suggested that this circumstance in one of them has been propagated by that of another, through any occult principle, or whatever else such an agency may be called. Had the case not presented at once, and in so direct and striking a manner, a sufficient cause for the effects observed, then we doubt not, that, perhaps, individuals would relieve themselves of any present difficulty, and attribute what they could not readily explain, to the operation of a principle having as little evidence of its entity as atmospheric contagion itself. But the sun is too glorious, too resplendent an object to be overlooked, and its effects are too immediate, to permit the possibility of the most unreflecting, not marking its relation as cause to the effect observed. But, unfortunately, the relation between widely spread diseases or epidemics, as they are called, and circumstances connected with the agencies before referred to, is not so striking—though it is as close. There is no object so bright to draw the same attention to it, and to proclaim it from east to west, from the dawn of morning till the fall of evening, like that luminary dispersing light as he appears to traverse the heavens. Yet there is room to believe that the presence of epidemics is always accompanied, or shortly preceded, by circumstances, which, though by reason of their less striking character, and less immediate operation, are sometimes overlooked or neglected, yet do exist, and, were inquiry made by those able for the purpose, doubtless would be found.