There is an old term, as old as the good old English physician, Sydenham--_constitution of the atmosphere_--and to what else than to some inscrutable condition of the element in which we live, and breathe, and have our being--in fact to an atmospheric poison beyond our ken, can we ascribe the terrific gambols of such a destroyer. 'Tis on record, that when our armies were serving in the pestilential districts of India, hundreds, without any noticeable warning, would be taken ill in the course of a single night, and thousands in the course of a few days, in one wing of the army, while the other wing, upon different ground, and consequently under a different current of atmosphere, although in the course of the regular necessary communication between troops in the field, would remain perfectly free from the disease. It would then cease as suddenly and unaccountably as it began,--attacking, weeks after, the previously unscathed division of the army, or not attacking it at all at the time, yet returning at a distant interval, when all traces of the former epidemic had ceased, and committing the same devastation. Now, will any man, not utterly blinded by prejudice, candidly reviewing these facts, pretend to say, that this could be a personal contagion, cognizable by, and amenable to, any of the known or even supposable laws of infection--that the hundreds of the night infected one another, or that the thousands of the few days owed their disease to personal communication,--as well affect to believe that the African Simoon, which prostrates the caravan, and leaves the bones of the traveller to whiten in the sandy desert, could be a visitation of imported pestilence.