Visual Education (Jan 1923-Dec 1924)

u Visual Education Chief among the followers of the comets by the method of the dry plate has been Professor E. . E. Barnard, who began this work at the Lick Observatory in 1889 and has continued it assiduously at the Yerkes Observatory since 1897. The Temperamental Comet Many of the comets are such lemperamental bodies that it is necessary that they should be photographed every hour at some station on the earth in order to get a complete record ; and many of their changes still defy explanation. Comets will sometimes shed their tails, or shake them, so far as appearance goes, or indulge in several of them at the same time — some of them pointing straight away from the sun, as they should — while others saucily poke a tail right toward the sun, apparently with impunity. Some are stolid and uninteresting, but even these may develop eccentricities which would escape the eye but are visible on the photographic plate. Occasionally comets split into two or three parts which seem to go on as separate comets. And of variety there is no end. The Camera in Astronomical Discovery Comets are now often discovered by photography, a little patch of haze appearing on the plate where the charts show no nebula. Now, if the astronomer had only one such plate this might be some little smudge or defect on the photographic plate, or possibly a little stray daylight might have fallen upon the plate through the slot where the slide is drawn. Every little inequality of the surface will pi'oduce artificial comets, many of them very lifelike. Accordingly, the wise astronomer always, has twin telescopes at work for him while he is making an exposure. Then if the little patch of fuzz is found on one of the plates only, he knows that it is a defect. Otherwise, he must make several photographs of the region to see if the object moves; because if it is stationaiy it certainly is not a' comet. It is one of Nature's inexorable requirements of a comet or of a planet — or, we may add, of any celestial object — that it be always and everlastingly ''on the move." There is no heaven which offers rest for celestial objects. Photographing a Meteor Shower When a regularly recurrent comet permanently disappears COMET MOREHOUSE A« photographed on Novembor 16, 1908. with the Bruce telescope, by E. E. Barnard Though scarcely reaching visibility to the naked eye, this comet was photographically unusually active and displayed many freakish peculiarities. Notice in the central part of the tail the ragged appearance of the receding gases, which are those of hydrogen, carbon and nitrogen, in different combinations. The tall could be traced for 10 million miles on the negative, and it that time the comet's distance from the earth was 132 million miles. I he light of the stars shone undimmed through a thick nen of a million miles of this filmy tail. COMET BROOKS As photographed with the Bruce telesccpe, by E. E. Barnard, on October 23, 1911 This comet was visible to the naked eye for over four months — an unusually long time. At first it was of very quiet demeanor, but it developed much activity when it was nearest the sun, at about the date of this picture. The many fine and wavy streamers appear as though the tail had been combed with a coarse comb, with an undulating motion. The appearance changed greatly from night to night. The tail could be traced for 26° on a negative made on this date, corresponding to more than 35 million miles. The head was about 300,000 miles in diameter at the time of the picture.