56 



KNOWLEDGE. 



[Mabcii 1, 1895. 



first-class observer, the Eev. W. E. Dawes. From these 

 designs we gather some further details. The Lake of the 

 Sun is no longer simply a circular dot. It is elongated, 

 and occasionally irregular in form : and ahke iu the 

 drawings of Kaiser, Lockyer, and Dawes, we meet witli 

 a new feature, now so familiar to us under the name of 

 " canal," a narrow line linking the Oculus to the outer sea 

 towards the east. 



It is, indeed, as the focus of a " canal " system of its 

 own that the Lake of the Sun has much of its importance 

 to us. Mars is dotted over with " lakes " from which 

 " canals " appear to radiate, but none of them have the 

 importance of the Lake of the Sun. In other cases it is 

 a question whether the "lake" is due to the "canals," 

 or the "canals" to the " lake." In this case the prhnary 

 importance of the " lake " is manifest. 



There is no need to refer to the less favourable oppo- 

 sitions, for not only was Mars then further from us, 

 but the district we are considering was presented under a 

 more or less foreshortened aspect. But in 1877 we had 

 again a very favourable opposition, and a great number 

 of observers were at work on the planet — Green and 

 Schiaparelli in particular. The drawings of the former. 



Fio. 2. — Key-map of the laeus Solis region, according 

 SchiapareUi. From Flaramarion's " Mars," p. 361. 



to 



confessedly the best that have yet been published. Nor 

 is this fact in any way contradictory of the criticisms _ that 

 have been passed on certain of his drawings of individual 

 portions. 



In Fig. 2 we have a portion of his chart of Mars, 

 published as the result of nine years' work, and showing 



the region with 

 which we are 

 more particularly 

 concerned. In 

 Fig. 3 we have 

 a drawing made 

 by him of Thau- 

 masiaon.JuneOth, 

 1890. 



Here a new de- 

 tail is shown. Be- 

 side the numerous 

 canals radiating 

 off from the Lake 

 of the Sun in all 

 ' bridge" some 



published in Vol. XLIV. of Memoirs of the Eoi/al Astro- 

 nomical Society, still remain the most truthful and life-like 

 pictures of Mars that have yet been published, though 

 later observers have added many details which escaped 

 even Mr. Green's great powers of sight. The second figure 

 in our plate is by Schiaparelli, under date September '2Cth, 

 1877. The third is also by the same observer, and was 

 made at the next opposition, on November 11th, 1879, when 

 Mars was again suitably presented for the study of this 

 region, and when the " canal " system had undergone, as 

 the sketch unmistakably shows, a most extraordinary 

 development. 



Diu-ing the next two or three oppositions the chief work 

 on Mars was effected by the industry of the great Italian 

 astronomer, and he brought out chart after chart, each show- 

 ing a distinct advance on its predecessor, and each depending 

 on a fine series of careful micrometric measures for the 

 positions of the principal points. It is beyond all doubt 

 due to the fact that they are based on meastires, not on eye 

 estimations only, and that as one of the best living double 

 star observers, Schiaparelli was a past master in the use of 

 the micrometer, that his charts of the entire planet are 



Fig. 3.— The " Eve " of Mars, as drawn by 

 Schiaparelli. June 9th, 1890. From 

 Flammarioc's " Mars," p. 573. 



directions, the lake itself is crossed by 

 500 miles long and, perhaps, 50 wide. 



We now come to the last two oppositions. The former 

 of these is illustrated in our plate by two strongly contrasted 

 pictures ; Nos. 4 and 5 — the former by Mr. Hussey, 

 drawn on August 17th, 1892, with the aid of the great 

 thirty-six inch refractor of the Lick Observatory ; the 

 latter by M. Gniot, on September 6fch, 1892, with the nine- 

 inch telescope of M. Flammarion's observatory at Juvisy. 

 No. i was published in Astronomy ami Astro-Plujsirs for 

 October, 1892 ; No. 5 in L' Astronomic for November, 1S92. 

 The four remaining designs represent the oppositions just 

 past, and I am indebted for them to the kindness of the 

 respective artists. They were taken as follows : — 



No. 6 by Herr L. Brenner, Manora, Istria, on September 

 14th, 1891. 



No. 7 by Mr. Stanley Williams, Brighton, on September 

 23rd, 1894. 



No. 8 by Mr. Bernard Cammell, Wokingham, on 

 September 27th, 1894. 



No. 9 by M.E.M.Antoniadi, Paris, on November 1st, 1894. 

 The most casual 

 glance at the nine 

 drawings given in the 

 plate shows that, 

 whilst it is absolutely 

 clear that all the ob- 

 servers were watching 

 the same district of 

 the planet , and though 

 all agree in certain 

 broad features, the 

 differences in detail 

 are neither few nor 

 slight. 



Do these differ- 

 ences represent real 

 facts, or are they 

 simply due to imper- 

 fect seeing and im- 

 perfect drawing? 

 That much of the 

 diversity in sketches 



of Mara rests with the observer, and with him entirely, has 

 often been shown, and in particular by M. Flammarion in 

 his classical work. One of the instances which he adduces of 

 manifest " personal equation " relates to this very district of 

 Thaumasia. Father Secchi made a drawing of Mars at 



Fia. 4.— The " Eye " of Mars, as 

 drawn by Secchi, Oct'ober Ibth, 1862, at 

 7h. 24m"., Greenwich Mean Time. From 

 Flammarion's " Mars," p. 549. 



