The four last of the forms of disease, that have been mentioned, have been very properly called intestinal states of fever. They nearly accord, in their greater or less degrees of violence and danger, with the first four states of fever which occupy the blood-vessels, and in the order in which both of them have been named. I shall illustrate this remark by barely mentioning the resemblance of the yellow fever to the dysentery, in being attended with costiveness in its first stage, from a suspended or defective secretion or excretion of bile, and in terminating very generally in death, when not met by the early use of depleting remedies. The variety in the forms and grades of the summer and autumnal disease, in different seasons, and their occasional changes into each other in the same seasons, are to be sought for in the variety of the sensible and insensible qualities of the atmosphere, of the course of the winds, and of the aliments of different years. II. The means of preventing the different forms of disease that have been mentioned, come next under our consideration. Happily for mankind, Heaven has kindly sent certain premonitory signs of the most fatal of them. These signs appear, I. Externally, in certain changes in previous diseases, in the atmosphere, and in the animal and vegetable creation. II. In the human body. 1. The first external premonitory sign that I shall mention is, an unusual degree of violence in the diseases of the previous year or season. Many proofs of the truth of this remark are to be met with in the works of Dr. Sydenham. It has been confirmed in Philadelphia, in nearly all her malignant fevers since the year 1793. It would seem as if great and mortal epidemics, like the planets, had satellites revolving round them, for they are not only preceded, but accompanied and followed, by diseases which appear to reflect back upon them some of their malignity. But there is an exception to this remark, for we now and then observe uncommon and general healthiness, before the appearance of a malignant epidemic. This was the case in Philadelphia, previously to the fevers of 1798 and 1799. I have ascribed this to the stimulus of the pestilential miasmata barely overcoming the action of weak diseases, without being powerful enough to excite a malignant fever. 2. Substances, painted with white lead, and exposed to the air, suddenly assuming a dark colour; and winds from unusual quarters, and unusual and long protracted calms, indicate the approach of a pestilential disease. The south winds have blown upon the city of Philadelphia, ever since 1793, more constantly than in former years. A smokiness or mist in the air, the late Dr. Matthew Wilson has remarked, generally precedes a sickly autumn in the state of Delaware.