engravings; for by no means are philosophical subjects better elucidated
than by the aid of the graphic art.]


_Longevity_.

The relative advantages of town and country, in point of salubrity, are
shown by the following table of deaths:--

1. In _great towns_, from 1-19 or 1-20, to 1-23 or 1-24.

2. In _moderate towns_, from 1-25 to 1-28.

3. In _small villages_ and the _open country_, from 1-35 or
1-40, to 1-50 or 1-60.

Thus, in London one person in 20 of the whole population dies annually;
while in the healthiest villages and open country, the rate of annual
mortality is not more than 1 in 55 or 60.


_Atmosphere of Theatres_.

Lavoisier, the French chemist, found, in a theatre, that, from the
commencement to the end of the play, the oxygen, or vital air, was
diminished in the proportion of from 27 to 21, or nearly one-fourth, and
was in the same proportion less fit for respiration than before.


_Butterflies_.