HISTORY OF 



liar malignity of the air thus suffering from ani- 

 mal putrefaction was, that the contagious steams 

 had produced spots on the very wall of their 

 wretched apartment : and Mr Boyle's own study, 

 which was contiguous to a pest-house, was also 

 spotted in the same frightful manner. Happily 

 for mankind, this disorder, for more than a cen- 

 tury, has not been known in our island ; and, for 

 this last age, has abated much of its violence, 

 even in those countries where it is most common. 

 Diseases, like empires, have their revolutions ; 

 and those which for a while were the scourge of 

 mankind, sink unheard of, to give place to new 

 ones, more dreadful, as being less understood. 



For this revolution in disorders, which has em- 

 ployed the speculation of many, Mr Boyle ac- 

 counts in the following manner : " Since," says 

 he, " there want not causes in the bowels of the 

 earth to make considerable changes amongst the 

 materials that nature has plentifully treasured up 

 in those magazines, and as those noxious steams 

 are abundantly supplied to the surface, it may not 

 seem improbable, that, in this great variety, some 

 may be found capable of particularly affecting the 

 human frame in a particular manner, and thus of 

 producing new diseases. The duration of these 

 may be greater or less, according to the lasting- 

 ness of those subterraneous causes that produced 

 them. On which account, it need be no wonder 

 that some diseases have but a short duration, and 

 vanish not long after they appear ; whilst others 

 may continue longer, as having under ground 



