! ON IMPROVING NATURAL KNOWLEDGE 27 



generation which could produce a Boyle, an 

 Evelyn, and a Milton. He might find the mud of 

 society at the bottom, instead of at the top, but I 

 fear that the sum total would be as deserving of 

 swift judgment as at the time of the Restora- 

 tion. And it would be our duty to explain 

 once more, and this time not without shame, that 

 we have no reason to believe that it is the 

 improvement of our faith, nor that of our 

 morals, which keeps the plague from our city ; 

 but, again, that it is the improvement of our 

 natural knowledge. 



We have learned that pestilences will only take 

 up their abode among those who have prepared 

 unswept and ungarnished residences for them. 

 Their cities must have narrow, unwatered streets, 

 foul with accumulated garbage. Their houses 

 must be ill-drained, ill-lighted, ill-ventilated. 

 Their subjects must be ill- washed, ill-fed, ill- 

 clothed. The London of 1665 was such a city. 

 The cities of the East, where plague has an 

 enduring dwelling, are such cities. We, in later 

 times, have learned somewhat of Nature, and 

 partly obey her. Because of this partial im- 

 provement of our natural knowledge and of that 

 fractional obedience, we have no plague ; because 

 that knowledge is still very imperfect and that 

 obedience yet incomplete, typhoid is our companion 

 and cholera our visitor. But it is not presumptuous 

 to express the belief that, when our knowledge is 



