to be unfit for such employment. There are no doubt reasons for this distinction, whether conclusive or not, but the classification is by no means above criticism, for within our own time Astronomy has been taken out of the category of the established or perfect sciences, and may be now cited as one of the best illustrations of a progressive science. Of course, there are established truths in Astronomy, and so there are in Chemistry and Physics, but Astronomy has now assumed a new character of progressiveness, and within the present generation it has surpassed all the other sciences in the rapidity and splendor of its advancement.
Not so many years ago it seemed as though astronomy were approaching, if it had not already reached, its final stage. The Sun and his family had been measured and weighed, the Moon tracked in all her motions, and the paths of comets determined. The younger Herschel had completed the survey of the heavens, which his father commenced, and, to all seeming, little remained to be ascertained about the universe. And yet, in the presence of the astronomy of our day, that of a few years ago looks crude and elementary. Newton made an epoch by bringing the movements of the planetary bodies under the demonstrated laws of terrestrial force; Kirchhoff and the spectroscopists have made a new era by subordinating stars, comets, and nebulae, to the laws of terrestrial chemistry. The recent physical explorations of the sun constitute one of the most thrilling chapters in all science. Nor have astronomers been content with the unquestioned acceptance of the older views respecting the planetary scheme. Not Ptolemy alone, or Hipparchus, Galileo, Kepler, and Newton, but even the elder and younger Herschel, would stand aghast at the change of opinion that has been wrought regarding the members of the solar system. Jupiter and Saturn, so long considered as merely large specimens of habitable worlds, have taken their place in a higher order of orbs, while satellites, formerly thought to be set as lights to illumine their primaries, have been raised almost to the dignity of planets. Even more surprising have been the discoveries made respecting comets and meteors, while modern inquiries have not stopped short of the domain of the so-called fixed stars, so that the whole scheme of the stellar universe begins to present a new aspect.
Astronomical science, in short, has been enlarged and reshaped in the nature and scope of its problems, and has entered into a new epoch in our own time which opens to us even a grander future than was disclosed either to Copernicus or to Newton.
As was quite unavoidable, this recent revolution or extension of the science has left behind the old teachers, and created a demand for new men, who can deal with the subject in its more novel and extended aspects. And, as supply follows demand in the intellectual as well as the commercial world, the expounders of the new dispensation