h, except for the progress of natural knowledge, we should not have
been able to make even the tools by which these machines are
constructed. And, further, it would be necessary to add, that although
severe fires sometimes occur and inflict great damage, the loss is very
generally compensated by societies, the operations of which have been
rendered possible only by the progress of natural knowledge in the
direction of mathematics, and the accumulation of wealth in virtue of
other natural knowledge.

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 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 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
improvement 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, typhus is our companion and cholera our
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 centuries of freedom from typhus and
cholera, as she now gratefully reckons her two hundred years of
ignorance of that 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 the facts? Surely, t