the observations I have had occasion to make upon this town and
country.

The air of Boulogne is cold and moist, and, I believe, of
consequence unhealthy. Last winter the frost, which continued six
weeks in London, lasted here eight weeks without intermission;
and the cold was so intense, that, in the garden of the
Capuchins, it split the bark of several elms from top to bottom.
On our arrival here we found all kinds of fruit more backward
than in England. The frost, in its progress to Britain, is much
weakened in crossing the sea. The atmosphere, impregnated with
saline particles, resists the operation of freezing. Hence, in
severe winters, all places near the sea-side are less cold than
more inland districts. This is the reason why the winter is often
more mild at Edinburgh than at London. A very great degree of
cold is required to freeze salt water. Indeed it will not freeze
at all, until it has deposited all its salt. It is now generally
allowed among philosophers, that water is no more than ice thawed
by heat, either solar, or subterranean, or both; and that this
heat being expelled, it would return to its natural consistence.
This being the case, nothing else is required for the freezing of
water, than a certain degree of cold, which may be generated by
the help of salt, or spirit of nitre, even under the line. I
would propose, therefore, that an apparatus of this sort should
be provided in every ship that goes to sea; and in case there
should be a deficiency of fresh water on board, the seawater may
be rendered potable, by being first converted into ice.

The air of Boulogne is not only loaded with a great evaporation
from the sea, increased by strong gales of wind from the West and