SECTION OF THE PRIMITIVE MOUNTING
SPECTRAL IMAGES OF STARS, THE UPPER LINE SHOWING HOW THEY APPEAR WITH THE EYE-PIECE PUSHED IN, THE LOWER WITH THE EYE-PIECE DRAWN OUT
THE GREAT REFRACTOR OF THE NATIONAL OBSERVATORY AT WASHINGTON
THE "BROKEN-BACKED COMET-SEEKER"
NEBULA IN ORION
DIP OF THE MAGNETIC NEEDLE IN VARIOUS LATITUDES
PROFESSOR LANGLEY'S AIR-SHIP
In preparing and issuing this collection of essays and addresses, the author has yielded to what he could not but regard as the too flattering judgment of the publishers. Having done this, it became incumbent to do what he could to justify their good opinion by revising the material and bringing it up to date. Interest rather than unity of thought has determined the selection.
A prominent theme in the collection is that of the structure, extent, and duration of the universe. Here some repetition of ideas was found unavoidable, in a case where what is subst
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