It should be recognized that Professor Young, of [Page 54] Princeton, is the most successful operator in this recent realm of science.  He already proposes to correct the former estimate of the sun’s axial revolutions, derived from observing its spots, by the surer process of observing accelerated and retarded light.

Within a very few years this wonderful instrument, the spectroscope, has made amazing discoveries.  In chemistry it reveals substances never known before; in analysis it is delicate to the detection of the millionth of a grain.  It is the most deft handmaid of chemistry, the arts, of medical science, and astronomy.  It tells the chemical constitution 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.

[Page 55] 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.

[Page 56]
 “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.

[Page 57] 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.