Illustrations 



FACING 

 PAGE 



JUPTTM ' 23 



SATURN, NOTEMBER 19, 1911 23 



Photo: Professor E. E. Barnard, Yerkes Observatory. 



Tur SPECTROSCOPE, AN INSTRUMENT FOR ANALYSING LIGHT; IT PROVIDES 



-<TiKViNci SUBSTANCES (Coloured Illustration) . . 24 



THE MOON ... .... 28 



MAB> 29 



Drawings by Professor Percival Lowell. 



THK MOON, AT NINE AND THREE QUARTER DAYS . . .29 



A MAP or THE CHIEF PLAINS AND CRATERS OF THE MOON . 



A DIAGRAM OF A STREAM OF METEORS SHOWING THE EARTH PASSING 



THROUGH THEM ... ... .32 



COMET, SEPTEMBER 29, 1908 . . .33 



Photo: Royal Observatory, Greenwich. 



COMET, OCTOBER 3, 1908 33 



Photo: Royal Observatory, Greenwich. 



TYPICAL SPECTRA . . ... . . . . . .36 



Photo: Harvard College Observatory. 



A NEBULAR REGION SOUTH OF ZETA ORIONIS ..... 37 



Photo: Mount Wilson Observatory. 



K CLUSTER IN HERCULES ........ 37 



Photo: Astrophysical Observatory, Victoria, British Columbia. 



THE GREAT NEBULA IN ORION 40 



Photo: Yerkes Observatory. 



GIAXT SPIRAL NEBULA, MARCH 23, 1914 41 



Photo: Lick Observatory. 



A SPIRAL NEBULA SEEN EDGE-ON 44 



Photo: Mount Wilson Observatory. 



IOO-INCH TELESCOPE, MOUNT WILSON 45 



Photo: H. J. Shepstonr. 



THE YERKES 40-1 NCH REFRACTOR 48 



THE DOUBLE-SLIDE PLATE-HOLDER ON YERKES 40-lNCH REFRACTING 



TELESCOPE 49 



Photo: H. J. Shepstone. 



