PREFACE.

by tlie secret charm which a constant intercourse with nature never failsto yield.

The twentieth chapter contains the history of the Telescope. The re-searches of Van Swinden have recently contributed to throw much inte-resting light upon the original invention of that instrument.

The twenty-first chapter, which completes the work, is devoted to acondensed account of the progress of researches in Stellar Astronomy.The labours of modem enquirers in this department of AstronomicalScience have led to some conclusions of a highly interesting and importantnature. The existence of a sensible parallax in the fixed stars—a questionwhich has occasioned much anxious investigation from the time of Coper­ nicus down to the present day—has at length been definitively establishedin several instances by the labours of Bessel, Henderson, Struve, Peters,and Maclear. It is now ascertained beyond all doubt, that light, travellingat the rate of 193,000 miles in a second, would require three years anda half to traverse the space between one of the nearest of those lumina-ries and the earth! The motion of the solar system in space, is anotherof those sublime conclusions which have been established by the re-searches of modern astronomers. It appears from the labours of SirWilliam Herscliel and his successors on this subject, that not only dothe satellites move round the planets, and the planets round the Sun, butthat the Sun, with his whole cortege of planets and satellites, is beingconstantly transported through space to a determinate point iii the heavens,revolving, in all probability, round the centre of gravity of some yastsystem of suns, of which it forms one of the constituent members. Thusthe farther the human mind is allowed to penetrate into the mechanismof the physical universe, the more overwhelming is the impression pro-duced of the surpassing grandeur of its movements, and the more exaltedis the conception formed of the Omnipotent Being who constantly pre-sides over its countless arrangements.

To the student of Celestial Physics, the researches of astronomers onDouble Stars offer a high degree of interest, inasmuch as they serve todemonstrate that the law of Gravitation, as announced by Newton, actuallyprevails in the mutual action of those remote bodies of the universe. Thephenomena of Nebulae excited little interest among astronomers until theyattracted the attention of Sir William Herschel . The vast extent ofthat astronomer’s observations of those objects, and the originality of hisviews on their physical constitution, had the effect of elevating them toa high degree of importance in sidereal astronomy. The subsequentlabours of Sir John Herschel and LordRosse, in the same field of enquiry,have materially contributed to the advancement of our knowledge respect-ing those wonderful structures.

After a rapid view of the progress of research on the various subjectsabove mentioned, allusion is made to the labours of astronomers on thephysical constitution of the Milky Way and the Distribution of the Starsin space. The chapter concludes with a brief account of the interesting