It would be easy to multiply illustrations in proof of the great
practical importance of accurate scientific designations, drawn from
astronomical observations, in various relations connected with
boundaries, surveys, and other geographical purposes; but I must hasten
to
3. A third important department, in which the services rendered by
astronomy are equally conspicuous. I refer to commerce and navigation.
It is mainly owing to the results of astronomical observation, that
modern commerce has attained such a vast expansion, compared with that
of the ancient world. I have already reminded you that accurate ideas
in this respect contributed materially to the conception in the mind
of Columbus of his immortal enterprise, and to the practical success
with which it was conducted. It was mainly his skill in the use of
astronomical instruments--imperfect as they were--which enabled him, in
spite of the bewildering variation of the compass, to find his way
across the ocean.
With the progress of the true system of the universe toward general
adoption, the problem of finding the longitude at sea presented itself.
This was the avowed object of the foundation of the observatory at
Greenwich;[A] and no one subject has received more of the attention of
astronomers, than those investigations of the lunar theory on which
the requisite tables of the navigator are founded. The pathways of the
ocean are marked out in the sky above. The eternal lights of the heavens
are the only Pharos whose beams never fail, which no tempest can shake
from its foundation. Within my recollection, it was deemed a necessary
qualification for the master and the mate of a merchant-ship, and even
for a prime hand, to be able to "work a lunar," as it was called. The
improvements in the chronometer have in practice, to a great extent,
superseded this laborious operation; but observation remains,
and unquestionably will for ever remain, the only dependence for
ascertaining the ship's time and deducting the longitude from the
comparison of that time with the chronometer.
[Footnote A: Grant's _Physical Astronomy_, p. 460.]
It may, perhaps, be thought that astronomical science is brought already
to such a state of perfection that nothing more is to be desired, or at
least that nothing more is attainable, in reference to such practicable
applications as I have described. This, however, is an idea which
generous minds will reject, in this, as in every other department of
human knowledge. In astronomy, as in every thing else, the discoveries
already made, theoretical or practical, instead of exhausting the
science, or putting a limit to its advancement, do but furnish the means
and instruments of further progress. I have no doubt we live on the
verge of discoveries and inventions, in every department, as brilliant
as any that have ever been made; that there are new truths, new facts,
ready to start into recognition on every side; and it seems to me there
never was an age, since the dawn of time, when men ought to be less
disposed to rest satisfied with the progress already made, than the age
in which we live; for there never was an age more distinguished for
ingenious research, for novel result, and bold generalization.
That no further improvement is desirable in the means and methods of
ascertaining the ship's place at sea, no one I think will from
experience be disposed to assert. The last time I crossed the Atlantic,
I walked the quarter-deck with the officer in charge of the noble
vessel, on one occasion, when we were driving along before a leading
breeze and under a head of steam, beneath a starless sky at midnight, at
the rate certainly of ten or eleven miles an hour. There is something
sublime, but approaching the terrible, in such a scene;--the rayless
gloom, the midnight chill,--the awful swell of the deep,--the dismal
moan of the wind through the rigging, the all but volcanic fires within
the hold of the ship. I scarce know an occasion in ordinary life in
which a reflecting mind feels more keenly its hopeless dependence on
irrational forces beyond its own control. I asked my companion how
nearly he could determine his ship's place at sea under favorable
circumstances. Theoretically, he answered, I think, within a
mile;--practically and usually within three or four. My next question
was, how near do you think we may be to Cape Race;--that dangerous
headland which pushes its iron-bound unlighted bastions from the
shore of Newfoundland far into the Atlantic,--first landfall to
the homeward-bound American vessel. We must, said he, by our last
observations and reckoning, be within three or four miles of Cape Race.
A comparison of these two remarks, under the circumstances in which we
were placed at the moment, brought my mind to the conclusion, that it is
greatly to be wished that the means should be discovered of finding the
ship's place more accurately, or that navigators would give Cape Race a
little wider berth. But I do not remember that one of the steam packets
between England and America was ever lost on that formidable point.
It appears to me by no means unlikely that, with the improvement of
instrumental power, and of the means of ascertaining the ship's time
with exactness, as great an advance beyond the present state of art and
science in finding a ship's place at sea may take place, as was effected
by the invention of the reflecting quadrant, the calculation of lunar
tables, and the improved construction of chronometers.