IMPROVING NATURAL KNOWLEDGE 19 



But the plague ? My Lord Brouncker's observation would 

 not, I fear, lead him to think that Englishmen of the nineteenth 

 century are purer in life, or more fervent in religious faith, 

 than the generation which could produce a Boyle, an Evelyn, 

 and a Milton. He might find the mud of society at the 5 

 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 

 Restoration. 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 10 

 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 ungar- 

 nished residences for them. Their cities must have narrow, 15 

 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, 20 

 have learned somewhat of Nature, and partly obey her. Be- 

 cause of this partial improvement of our natural knowledge 

 and of that fractional obedience, we have no plague; be- 

 cause that knowledge is still very imperfect and that obedience 

 yet incomplete, typhus is our companion and cholera our 25 

 visitor. But it is not presumptuous to express the belief 

 that, when our knowledge is more complete and our obedience 

 the expression of our knowledge, London will count her cen- 

 turies of freedom from typhus and cholera, as she now grate- 

 fully reckons her two hundred years of ignorance of that 30 

 plague which swooped upon her thrice in the first half of the 

 seventeenth century. 



Surely, there is nothing in these explanations which is not 

 fully borne out by facts ? Surely, the principles involved in 



