In the _Fourth Section_, the Author, in conformity to the Custom of those that write of Feavers, discourses of the _Small-pox_; and _First_, examining the cause of this sickness and its universality, delivers his peculiar opinion of the bloud's endeavouring a Renovation or a New Texture (once at least in a Mans life) and is inclin'd to preferr the same to the received doctrine of its malignity. _Then_, having laid down, for a foundation of the Cure, the two times, of _Separation_ and _Expulsion_, he argues as well against too high an Ebullition or too hasty a separation (by a hot diet or high Cordials) as against too languid a one (by Blooding, Purges, and Cooling medicines.) The like he does to the Time of _Expulsion_, forbidding _both_ immoderate Heat (whereby Nature's expelling operation is disturbed by a precipitated and too thick a crowd of the protruded pustuls,) _and_ too much Cooling, whereby due Expulsion is hindred. In short, he advises, to permit Nature to do her own work, requiring nothing of the Physician, but to regulate her, when she is exorbitant, and to fortifie her, when she is too weak. He concludes all, with delivering a Model of the Method, he would use for his own only Son, if he should fall into this Sickness. * * * * * Advertisement. _Whereas 'tis taken notice of, that several persons perswade themselves, that these_ Philosophical Transactions _are publish't by the_ Royal Society, _notwithstanding many circumstances, to be met with in the already publish't ones, {214} that import the contrary; The Writer thereof hath thought fit, expresly here to declare, that that perswasion, if there be any such indeed, is a meer mistake; and that he, upon his_ Private _account (as a Well-wisher to the advancement of usefull knowledge, and a Furtherer thereof by such Communications, as he is capable to furnish by that Philosophical Correspondency, which he entertains, and hopes to enlarge) hath begun and continues both the composure and publication thereof: Though he denies not, but that, having the honour and advantage of being a_ Fellow _of the said_ Society, _he inserts at times some of the Particulars that are presented to them; to wit, such as he knows he may mention without offending them, or transgressing their Orders; tending only to administer occasion to others also, to consider and carry them further, or to Observe or Experiment the like, according as the nature of such things may require._ * * * * * Printed with Licence for _John Martyn_, and _James Allestry_, Printers to the Royal Society. 1666. {215} * * * * * _Numb._ 13. PHILOSOPHICAL _TRANSACTIONS._ * * * * * _Munday_, _June_ 4. 1666. * * * * * The Contents.