6. _Cold._ Its action, in exciting the disease, depended upon the diminution of the necessary and natural heat of the body, and thereby so far destroying the equilibrium of the system, as to enable the miasmata to produce excessive or convulsive motions in the blood-vessels. The night air, even in the warm month of September, was often so cool as to excite the disease, where the dress and bed-clothes were not accommodated to it. It was excited in one case by a person's only wetting his feet, in the month of October, and neglecting afterwards to change his shoes and stockings. Every change in the weather, that was short of producing frost, evidently increased the number of sick people. This was obvious after the 18th and 19th of September, when the mercury fell to 44° and 45°. The hopes of the city received a severe disappointment upon this occasion, for I well recollect there was a general expectation that this change in the weather would have checked the disease. The same increase of the number of sick was observed to follow the cool weather which succeeded the 6th and 7th of October, on which days the mercury fell to 43° and 46°. It was observed that those persons who were _habitually_ exposed to the cool air, were less liable to the disease than others. I ascribe it to the _habitual_ impression of the cool night air upon the bodies of the city watchmen, that but four or five of them, out of twenty-five, were affected by the disease. After the body had been heated by violent exercise, a breeze of cool air sometimes excited the disease in those cases where there had been no change in the temperature of the weather. 7. _Sleep._ A great proportion of all who were affected by this fever, were attacked in the night. Sleep induced what I have called debility from abstraction, and thereby disposed the miasmata which floated in the blood, to act with such force upon the system as to destroy its equilibrium, and thus to excite a fever. The influence of sleep as a predisposing, and exciting cause was often assisted by the want of bed-clothes, suited to the midnight or morning coolness of the air. 8. _Immoderate evacuations._ The efficacy of moderate purging and bleeding in preventing the disease, led some people to use those remedies in an excess, which both predisposed to the disease, and excited it. The morbid effects of these evacuations, were much aided by fear, for it was this passion which perverted the judgment in such a manner, as to lead to the excessive use of remedies, which, to be effectual, should only be used in moderate quantities. The disease appeared with different symptoms, and in different degrees, in different people. They both varied likewise with the weather. In describing the disease, I shall take notice of the changes in the symptoms, which were produced by changes in the temperature of the air.