er, sent in a watch which came within the limits, losing but
two minutes in a voyage to the West Indies; yet even this was an error
of thirty miles.

But, though chronometers have since been considerably improved, there
are difficulties in their preservation in good order which have made
it expedient to apply to other means; and the lunar tables of Mayer of
Gottingen, formed in 1755, and subsequently improved by Dr Maskelyne
and others, have brought the error within seven miles and a half.

Improvements of a very important order have also taken place in the
mariner's compass; the variation of the needle has been reduced to
rules, and some anomalies arising from the metallic attraction of the
ship itself, have been corrected by Professor Barlow's experiments.
The use of the marine barometer and thermometer have also largely
assisted to give notice of tempests; and some ingenious theories have
been lately formed, which, promising to give a knowledge of the origin
and nature of tempests, are obviously not unlikely to assist the
navigator in stemming their violence, or escaping them altogether.

The construction of ships for both the merchant and the public service
has undergone striking improvements within this century. Round sterns,
for the defence of a vessel engaged with several opponents at once;
compartments in the hold, for security against leaks; iron tanks for
water, containing twice the quantity, and keeping it free from the
impurities of casks; a better general stowage; provisions prepared so
as to remain almost fresh during an East Indian voyage; every means of
preserving health, suggested by science, and succeeding to the most
remarkable degree; a more intelligent system of shipbuilding, and a
constant series of experiments on the shape, stowage, and sailing of
ships, are among the beneficial changes of later times. But the one
great change--steam--will probably swallow up all the rest, and form a
new era in shipbuilding, in navigation, in the power and nature of a
navy, and in the comfort, safety, and protection of the crews in
actual engagement. The use of steam is still so palpably in its
infancy, yet that infancy is so gigantic, that it is equally difficult
to say what it may yet become, and to limit its progress. It will have
the one obvious advantage to mankind in general, of making the
question of war turn more than ever on the financial and mechanical
resources of a people; and thus increasing the nec