A compendium of astronomy; containing the elements of the science, familiarly explained and illustrated, with the latest discoveriesAdapted to the use of schools and academies, and of the general reader . somuch for angular measurements, as for aiding the pow-ers of vision in viewing the celestial bodies. When di-rected to the sun, it reveals to us various irregularities onhis disk not discernible by naked vision ; when turnedupon the moon or the planets, it affords us new and in-teresting views, and enables us to see in them the linea-ments of other worlds ; and when brought to bear uponthe f
A compendium of astronomy; containing the elements of the science, familiarly explained and illustrated, with the latest discoveriesAdapted to the use of schools and academies, and of the general reader . somuch for angular measurements, as for aiding the pow-ers of vision in viewing the celestial bodies. When di-rected to the sun, it reveals to us various irregularities onhis disk not discernible by naked vision ; when turnedupon the moon or the planets, it affords us new and in-teresting views, and enables us to see in them the linea-ments of other worlds ; and when brought to bear uponthe fixed stars, it vastly increases their number and re-veals to us many surprising facts respecting them. 88. How is an image formed by a concave mirror 1 How isthis image magnified 1 When is the instrument called a re-fracting and when a reflecting telescope ? For what pur-poses are telescopes chiefly employed ? 56 THE EARTH. 89. The Transit Instrument is a telescope, which isfixed permanently in the meridian, and moves only inthat plane. It rests on a horizontal axis, which consistsof two hollow cones applied base to base, a form unitinglightness and strength. The two ends of the axis rest Fig. m on two firm supports, as pillars of stone, for example, soconnected with the building as to be as free as possiblefrom all agitation. In figure 12, AD represents the tele- 89. What is a Transit Instrument ? On what supports doesit rest as represented in figure 12. Why are they made so firm?Describe all parts of the instrument. What is its use 1 Howused to regulate clocks and watches 1 What kind of time isshown when the sun is on the meridian ? How is this con-verted into mean tme ? Give an example. ASTRONOMICAL INSTRUMENTS. 5? scope, E, W, massive stone pillars supporting the horizontal axis, beneath which is seen a spirit level, (whichis used to bring the axis to a horizontal position,) and na vertical circle graduated into degrees and circle serves the purpose of pla
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectastronomy, bookyear18
