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THE USES OF ASTRONOMY.*

HE telescope may be likened to a wondrous Cyclopean eye endued with superhuman power, by which the astronomer extends the reach of his vision to the further heavens and surveys galaxies and universes compared with which the solar system is but an atom floating in the air. The transit may be compared to a measuring-rod which he lays from planet to planet and from star to star to ascertain and mark off the heavenly spaces and transfer them to his notebook. The clock is the marvellous apparatus by which he equalizes and divides into nicely-measured parts a portion of that unconceived infinity of duration, without beginning and without end, in which all existence floats as on a shoreless and bottomless sea.

In the contrivance and the execution of these instruments the utmost stretch of inventive skill and mechanical ingenuity has been put forth. To such perfection have they been carried that a single second of magnitude or space is rendered a distinctly visible and appreciable quantity. "The arc of a circle," says Sir J. Herschel," subtended by one second, is less than the two hundred thousandth part of the radius; so that on a

* From a discourse delivered at Albany on occasion of the inauguration of the Dudley Observatory, in that city, August 28, 1856.

| circle of six feet in diameter it would occupy no greater linear extent than 700 part of an inch, a quantity requiring a powerful microscope to be discerned at all." 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 a 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 2,850,000,000 of miles.

The object of an observatory erected and supplied with instruments of this admirable construction and at proportionate expense is 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 of objects to the determination of their distances, their time of passing the meridian, 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, in furnishing them with costly instruments, and in the support of the men of science employed in making, discussing and recording, for successive generations,

these minute observations of the heavenly bodies? In an exclusively scientific treatment of this subject, an inquiry into its utilitarian relations would be superfluous even wearisome. But on an occasion like the present you will not, perhaps, think it out of place if I briefly answer the questions, What is the use of an astronomical observatory? and What benefit may be expected from the operations of such an establishment in a community like ours?

In the first place, we derive from the observations of the heavenly bodies which are made at an observatory our only adequate measures of time and our only means of comparing the time of one place with the time of another. Our artificial timekeepers -clocks, watches and chronometers-however ingeniously contrived and admirably fabricated, are but a transcript, so to say, of the celestial motions, and would be of no value without the means of regulating them by observation. It is impossible for them, under any circumstances, to escape the imperfection of all machinery the work of human hands, and the moment we remove with our timekeeper east or west it fails us. It will keep home-time alone, like the fond traveller who leaves his heart behind him. The artificial instrument is of incalculable utility, but must itself be regulated by the eternal clockwork of the skies.

This single consideration is sufficient to show how completely the daily business of life is affected and controlled by the heavenly bodies. It is they, and not our mainsprings, our expansion-balances and our compensationpendulums, which give us our time. To reverse the line of Pope,

'Tis with our watches as our judgments: none
Go just alike, but each believes his own.

But for all the kindreds and tribes and tongues of men, each upon their own meridian, from the Arctic pole to the equator, from the equator to the Antarctic pole, the eternal sun strikes twelve at noon, and the glorious constellations far up in the everlasting belfries of the skies chime twelve at midnight-twelve for the pale student over his flickering lamp, twelve amid the flaming wonders of Orion's belt if he crosses the meridian at that fated hour; twelve by the weary couch of languishing humanity, twelve in the star-paved courts of the empyrean; twelve for the heaving tides of the ocean; twelve for the weary arm of labor; twelve for the toiling brain; twelve for the watching, waking, broken heart; twelve for the meteor which blazes for a moment and expires; twelve for the comet whose period is measured by centuries; twelve for every substantial, for every imaginary, thing which exists in the sense, the intellect or the fancy, and which the speech or thought of man, at the given meridian, refers to the lapse of time.

Not only do we resort to the observation of the heavenly bodies for the means of regulating and rectifying our clocks, but the great divisions of day and month and year are derived from the same source. By the constitution of our nature the elements of our existence are closely connected with the celestial times. Partly by his physical organization, partly by the habit-second nature— of the race from the dawn of creation, man as he is and the times and seasons of the heavenly bodies are part and parcel of one system. The first great division of time,

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