n of the sun, the movements taking place, the nature of
comets, and nebulae. By the spectroscope we know that the atmospheres
of Venus and Mars are like our own; that those of Jupiter and Saturn
are very unlike; it tells us which stars approach and which recede,
and just how one star differeth from another in glory and substance.

In the near future we shall have the brilliant and diversely colored
flowers of the sky as well classified into orders and species as
are the flowers of the earth.

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IV.

CELESTIAL MEASUREMENTS.

"Who hath measured the waters in the hollow of his hand, and meted
out heaven with the span? Mine hand also hath laid the foundation
of the earth, and my right hand hath spanned the heavens."--_Isa._
xl. 12; xlviii. 13.

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"Go to yon tower, where busy science plies
Her vast antennae, feeling thro' the skies;
That little vernier, on whose slender lines
The midnight taper trembles as it shines,
A silent index, tracks the planets' march
In all their wanderings thro' the ethereal arch,
Tells through the mist where dazzled Mercury burns,
And marks the spot where Uranus returns.

"So, till by wrong or negligence effaced,
The living index which thy Maker traced
Repeats the line each starry virtue draws
Through the wide circuit of creation's laws;
Still tracks unchanged the everlasting ray
Where the dark shadows of temptation stray;
But, once defaced, forgets the orbs of light,
And leaves thee wandering o'er the expanse of night."
OLIVER WENDELL HOLMES.

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IV.

_CELESTIAL MEASUREMENTS._

We know that astronomy has what are called practical uses. If a
ship had been driven by Euroclydon ten times fourteen days and
nights without sun or star appearing, a moment's glance into the
heavens from the heaving deck, by a very slightly educated sailor,
would tell within one hundred yards where he was, and determine
the distance and way to the nearest port. We know that, in all
final and exact surveying, positions must be fixed by the stars.
Earth's landmarks are uncertain and easily removed; those which
we get from the heavens are stable and exact.

In 1878 the United States steam-ship _Enterprise_ was sent to survey
the Amazon. Every night a "star party" went ashore to fix the exact
latitude and longitude by observations of the stars. Our real landmarks
are not the pillars we rear, but the stars millions of miles away.
All ou