circle of six feet in diameter, it would occupy no greater linear extent
than 1-5700 part of an inch, a quantity requiring a powerful microscope
to be discerned at all."[A] The largest body in our system, the sun,
whose real diameter is 882,000 miles, subtends, at a distance of
95,000,000 miles, but an angle of little more than 32; while so
admirably are the best instruments constructed, that both in Europe
and America a satellite of Neptune, an object of comparatively
inconsiderable diameter, has been discovered at a distance of 2,850
millions of miles.

[Footnote A: _Outlines_, § 131.]


UTILITY OF ASTRONOMICAL OBSERVATIONS.

The object of an observatory, erected and supplied with instruments of
this admirable construction, and at proportionate expense, is, as I have
already intimated, to provide for an accurate and systematic survey
of the heavenly bodies, with a view to a more correct and extensive
acquaintance with those already known, and as instrumental power
and skill in using it increase, to the discovery of bodies hitherto
invisible, and in both classes to the determination of their distances,
their relations to each other, and the laws which govern their
movements.

Why should we wish to obtain this knowledge? What inducement is there
to expend large sums of money in the erection of observatories, and in
furnishing them with costly instruments, and in the support of the men
of science employed in making, discussing, and recording, for successive
generations, those minute observations of the heavenly bodies?