SCIENCE-GOSSIP. 



249 



CHAPTERS FOR YOUNG ASTRONOMERS. 



By Frank C. Dennett. 



THE PLANET MARS. 



The planet Mars, being our nearest celestial 

 body of large magnitude, with the exception of the 

 moon, naturally attracts much attention. He is 

 in opposition to the sun about once in two years, 

 but is not always at that time an equally imposing 

 object. His apparent diameter then varies con- 

 siderably. At its best it reaches 2g"'5, but some- 

 times only 13". This variation is due to the 

 eccentricity both of the earth's orbit and that of 

 Mars, which causes considerable difference in the 

 distance separating the two planets at the time 

 of opposition. The most favourable oppositions, 

 when the planets are 

 closest to each other, 

 occur at intervals of 

 about fifteen years, 

 the next being in the 

 summer of 1907 ; but 

 at these times Mars 

 has always a southern 

 declination, which is 

 unfortunate for ob- 

 servers in northern 

 latitudes. Mars is 

 the only superior 

 planet which shows 

 anything like a dis- 

 tinct phase ; the gib- 

 bous phase being in 

 this case very marked, 

 both before and after 

 opposition. 



It was early ob- 

 served that Mars had 

 spots on his surface, 

 and as far back as 

 1659 Huygens dis- 

 covered the rotation- 

 from these marks. 

 The more brilliant- 

 portions of the planet, 

 which are usually 

 believed to be land, 

 have a bright reddish 

 tint, and cover the 

 greater area of the 

 disc. The darker sec- 

 tions, seas, as they 

 are called, have a 

 very decided greenish 

 or bluish tint. Some 

 observers have held 



the opinion that this may be a result of contrast. 

 These indications may be seen, under favourable 

 circumstances, with very moderate means, for an 

 excellent series of drawings were made some years 

 since by Mr. Charles Grover with a telescope of 

 only two inches aperture. The diagrams given 

 herewith were made in 1879 by myself with a 

 5j-inch silver-on-glass reflecting telescope, by 

 Calver. Speaking generally, the land and sea 

 outlines appear to be permanent, though slight 

 alterations are noticed from time to time. The 

 late Richard A. Proctor, Mr. N. E. Green, M. G. V. 

 Schiaparelli and others have charted the mark- 

 ings, and names have been assigned to them. 



Those used in this chapter for the different 

 regions shown on the accompanying illustra- 

 tions are taken from the chart of Mr. Green, 

 which most accurately shows the details. The 



Planet Mars. 



sketches include all parts of the planet. The 

 dark markings shown are: — 1, Dawes Forked Bay, 

 which at best is seen double, reminding one of a 

 serpent's tongue; 2, Burton Bay; 3, Herschel II. 

 Strait ; 4, Arago Strait ; 5, De La Rue Ocean ; 

 6, Newton Sea ; 7, Lambert Sea ; 8, Knobel Sea ; 

 9, Tycho Sea ; 10, Christie Bay ; 11, Terby Sea ; 

 12, Airy Sea ; 13, Campani Sea ; 14, Miraldi Sea ; 

 15, Pratt Bay; 16, Trouvelot Bay: 17, Maunder 

 Sea ; 18, Huggins Bay ; 19, Hooke Sea; 20, Oude- 

 man Sea; 21, Delambre Sea; 22, Kaiser Sea; 

 23, Main Sea : 24, Zollner Sea ■ w, Schmidt Bay ; 

 26 Flammarion Sea. 



The brighter portions, indicated by letters, 

 are :— a, South Polar Cap ; b, North Polar Cap ; 

 c, Phillips Island ; d, Jacob Land ; e, Beer 

 Continent ; f, Madle 

 Continent ; g, Rosse 

 Land; h, Secchi 

 Continent ; i, Webb 

 Land ; k, Le'grange 

 Peninsula ; I, Gill 

 Land ; m, * Noble 

 Cape ; 11, Burckardt 

 Land ; 0, Fontana 

 Land ; p, Herschel I. 

 Continent ; q, Cassini 

 Land; r, Dreyer 

 Island ; s, Lockyer 

 Land ; t, Hirst Island ; 

 h, Kunowski Land ; 

 y x , Proctor Cape ; 46, 

 Banks Cape. 



The bright ' ' island ' ' 

 in fig. 2, marked Y, is 

 not on Mr. Green's 

 chart, but is named 

 Pyrrhae Regis by 

 M. Schiaparelli. The 

 land around the south 

 of Terby Sea (fig. 3) 

 is Kepler Land, and 

 that to the north Co- 

 pernicus Land, and 

 the lake to the north 

 of Terby Sea is named 

 by M. Schiaparelli 

 Tithopius Lacus. 

 Hind Peninsula is the 

 narrow tongue run- 

 ning in between Flam- 

 marion Sea and Main 

 Sea, as shown on 

 fig. 7. 



M. Eugene An- 

 toniadi has found that 

 a comparison of all the drawings of Hind 

 Peninsula and Main Sea indicates a distinct 

 modification of outline during the present century. 

 There will be noticed very brilliant borders to 

 some of the seas, as in figs. 4, 5 and 8, which 

 seems to imply snow-capped mountain chains near 

 the coast, as in the case of our own great 

 mountain system, the Andes, which extend along 

 the western coast-line of South America. 



The rotation period of the planet Mars, ac- 

 cording to the calculation of the late Mr. 

 Richard Proctor, amounts to 24b. 37m. 22735s., 

 which it is obvious is only a little longer than 

 that of the earth ; therefore the same spots 

 come to the same positions a little later each 

 evening. 



(To be continued with other illustrations.) 



