DISCOVERY 



41 



fully illuminated, and thus observation of its surface 

 can be prosecuted for weeks and even months at a 

 stretch. At favourable oppositions Mars is only 34 to 

 40 million miles away — which is, cosmically speaking, 

 a trifling distance — yet the Martian disc never appears 

 so large as that of Jupiter. It is much nearer to us, 

 but its diameter is only about 4,200 miles — a little more 

 than half that of our own world. And in small tele- 

 scopes the disc is disappointingly small. Thus the 

 progress of Martian astronomy was at first slow. 



Before 1777, two facts alone had been ascer- 

 tained. In 1638 Fontana, of Naples, caught glimpses 

 of dusky markings on the little red disc, and his 

 observations were abundantly confirmed by Huyghens 

 in 1659, while in turn the Dutch astronomer's surmise 

 that the Martian day was not dissimilar to our own in 

 length was verified in 1666 by the elder Cassini, whose 

 determination of the period as 24 hours 40 minutes was 

 a remarkable appro.ximation to the truth at that early 

 stage of telescopic astronomy. In 1719, Maraldi, the 

 nephew of Cassini, detected at the poles of the planet 

 the two brilliant white spots which have since been 

 known as the polar caps. The systematic study of 

 Mars may be said to date from Herschel's significant 

 discovery of the variation in size of these polar spots in 

 accordance with the seasons. " I may well be per- 

 mitted to surmise," Herschel wrote in 1784, " that the 

 bright polar spots are owing to the vivid reflection of 

 light from frozen regions ; and that the reduction 

 of these spots is to be ascribed to their being exposed 

 to the Sun." 



Herschel's study of Mars was only a part of his 

 wider investigation of the structure of the Universe ; 

 and accordingly he made no systematic series of 

 drawings, nor did he attempt to chart the planet. 

 This was reserved for the famous German astronomer 

 Madler and his wealthy pupil Beer, whose survey of the 

 planet occupied them for nine years, from 1830 to 1839. 

 The telescope employed by Beer and Madler was a 

 comparatively small one — only four inches in aperture 

 — and only the larger surface-markings were charted 

 by them. But their work was continued during the 

 middle decades of the nineteenth century by a number 

 of observers of great skill and patience, chief among 

 whom was the English astronomer Dawes, from whose 

 drawings Proctor constructed in 1S70 the first detailed 

 map of Mars. 



The conception of our neighbour world which was 

 then current was summarised in Proctor's phrase — 

 " Mars, the miniature of our Earth." It was assumed not 

 only that the polar caps were massesof snow and ice, but 

 that the reddish-ochre portions comprising the greater 

 part of the planet's surface represented the continents, 

 while the blue-green areas were the oceans. It had long 

 been known that Mars had an atmosphere, and clouds 



and mists had occasionally been observed. Points of 

 difference between our Earth and Mars had, of Jcourse, 

 been noted — for instance, the much smaller area of the 

 Martian disc occupied by seas^but on the whole the 

 work of the earlier nineteenth-century observers seemed 

 to confirm Herschel's opinion that " the analogy be- 

 tween Mars and the Earth is perhaps by far the greatest 

 in the whole Solar System." 



A new era in the study of the planet was opened in 

 1877 when Schiaparelli, the greatest Italian observer of 

 last century, commenced at Milan his long-continued 

 series of observations. Something of a sensation was 

 caused by his announcement that the continental areas 

 were intersected by a number of straight dark lines, 

 to which he gave the name of canali. It subsequently 

 transpired that Dawes and Secchi had actually seen and 

 drawn some of these markings, but had simply classified 

 them as straits. To Schiaparelh, therefore, belongs 

 the honour of first recognising their true nature. At 

 each subsequent opposition, Schiaparelli detected new 

 canals, and in 1879 and again in 1881 he observed that a 

 number of them appeared to be double ; but it was not 

 till 1886 that Schiaparelli's discovery was confirmed by 

 Perrotin and Thollon, of the Nice Observatory. Within 

 the next decade, however, many observers, both in 

 Europe and America, succeeded in seeing and drawing 

 these strange markings; and as the canaHform 

 appearance was gradually estabhshed as a true char- 

 acteristic of the Martian disc, numerous theories were 

 advanced in explanation of it. Most of these, such as 

 the hypotheses that the canals represented mountain 

 chains or huge fissures of enormous breadth and 

 width, have only a certain historical interest. More 

 plausible was the view originally advanced by CeruUi, 

 of Teramo, developed by Newcomb and championed by 

 Maunder, that the phenomenon of the canals " grows 

 out of the spontaneous action of the eye in shaping 

 slight and irregular combinations of light and shade, 

 too minute to be separately made out, into regular 

 forms." This theory had a certain vogue for a con- 

 siderable time, but it may be said to have been dis- 

 credited by the observations of the past thirty years, 

 and more especially by the success of the observers at 

 the Lowell Observatory, in 1905 and at subsequent 

 oppositions, in photographing the more prominent 

 canals. 



Recognising the importance of clear and steady air 

 for study and interpretation of the Martian markings, 

 two of the ablest American astronomers inaugurated, 

 early in the last decade of the nineteenth century, 

 astronomical observatories of a novel type. In 1892 

 Professor W. H. Pickering commenced observations on 

 Mars from the Harvard College station at Arequipa, 

 on the slope of the Andes, in Peru, and this work he still 

 carries on at the Harvard branch observatory at 



