THE first and most considerable Symptom of the second Class, is a Fever, which (as was before said) was a constant Attendant upon the last Pestilence; although indeed the Infection seemed to kill some before the Blood and other Juices could rise into Fermentation; wherefore it may be taken for granted, that most Persons were accompanied with a Fever. But this Fever indeed was in some very low and concealed, though in others it appeared openly; and he must be but little acquainted in physical Practice, who hath not frequently observed, that in malignant Fevers their Beginnings are hardly discernable, being accompanied with no Heat, no Inequality of Pulse, and no Thirst, although secretly indicated by some other lurking Symptoms; and the Manner in which such Patients expire, demonstrates, that they could not be altogether free of a Fever. There are many Circumstances indeed which make it thus difficult in the Accession to discern its Approaches, as a Want of Turgescency of Blood in the Veins and Arteries, through Defect of Room for such Commotion and Depuration, or because the Blood is so thin, crude, and degenerate, that it cannot but with Difficulty ferment and grow hot; or because the pestilential _Miasmata_ seem at their first Insinuation so friendly to the Constitution, as to stir up no remarkable Alteration in the Blood; or from its cold and styptick Quality, retarding or suppressing such an Agitation. WHEREFORE no Body should conjecture, that there is no Fever at all, where its manifest Symptoms do not immediately appear; but it most commonly happened otherwise during the late Contagion, for that discovered Signs apparent enough of its Presence, such as extream Inquietude, a most intense Heat outwardly, attended with unquenchable Thirst within, Dryness, Blackness of the Tongue, intolerable Heat of the _Præcordia_, and all other usual Concomitants of a Fever’s Accession. AS to the Fever’s Exacerbations and Remissions, it appeared by constant Experience, that sometimes they were erratick and changeable, and at others continued, without any Intervals; and it was also customary to meet with some that wholly remitted for 8, 10, or 12 Hours. The Alternations likewise of Heat and Cold were very various, and with some would change several Times in one Hour, and with others the Periods would be at much greater Distances; so also the recurring Accessions were sometimes milder, and at others more severe. Those who with great Difficulty went through the first Paroxysm, could bear the second with Ease, as being much milder; whereas again the third or fourth Accession would be with intolerable Vehemence and Fury: And at other Times the first Fit would be gentle, and the subsequent very severe and intense; and truly such was the Uncertainty and Disguise of this insidious Enemy, that nothing could be prognosticated of its Attacks or Cruelty. BUT to come at some tolerable Notion of the Reason for such Uncertainty; it is to be enquired,