Aprh., 1902.] 



KNOWLEDGE 



83 



the other worlds have not the self-same positions for 

 different observers. A query of scepticism might be 



Fio. 4.— Mars in 1900-1901. 



attached to a fugitive, uou-recurring impression of a dark- 

 line splitting a planetarv disc. But if an analogous 

 impres.'iion occur, at^'aiu an 1 again, on the same night, and 

 always at the same poiut oMhe jilanet's surface, shifting 



Mr. E. W. Maunder pointed out what he thought was the 

 reason of the visibility of the Martian canals, namelv, that 

 different dark points on the planet's surface, too small to 

 be appreciated individually, produced on the retina the 

 idea of diffused lines. Mr. Maunder predicted then that 

 the next discovery on Mars would be that of small dots, or 

 " lakes." The forecast has been since verified to the letter. 

 In 18il5, we had Mr. Losvell's numerous dots or " oases," 

 while last year my frieud, M. G. Millochau, the able and 

 industrious astronomer of the Meudon Observatorv, using 

 the largest refractor in Europe, the noble 33-inch object- 

 glass of the Brothers Henry, wrote : — " I have seen the 

 canals hke some sort of chaplet of small, dark, irregular 

 masses." 



The resolution of the canals into their components is 

 evidently reserveil to jiowerful instruments only. 



Another significant fact about the canals is that many 

 of them form the boundaries of half-tones. This dis- 

 covery, due to the late Mr. Green, has been verified 

 in 18!19 by the Rev. P. H. Kempthome, of Wellington 

 College, and, subsecjuently, by a vcrj' great number 

 of first-class observers. As will be gathered by an 

 inspection of Figs. 1 to 4, embracing the whole of 

 the writer's impressions in 1900-1901, a considerable part 

 of the planet's northern hemisphere was covered with a 

 delicate shading, whose southern edge was limited by the 

 canals " Nasamou," Nilosyrtis, Protouilus, Deuteronilus, 

 Gehon II., Tauais, Erebus, Styx, Chaos, Hyblneus, and 

 Eunostos. The intensity of this half-tone was far from 

 uniform, being lightest in Cydonia, great in Phlegi-a, be- 

 tween the Hades and Styx, and very great in Utopia, where 

 it formed a " marsh," to which was given the name of 

 " Copais Lacus." Generally, the canals are very difficult 

 objects, being perceptible by rare glimpses only. The 

 appearance of Mars on the accompanying Plate* is the 

 summation of the successive fugitive impressions shown 



221i. 8m. 22h. 21m. 22h. 3-tm. 22h. 46ni. 221i. 51m. 



Duration = 23. Duration ^= Js. Duration == Js. Duration = Is. Dimition =• is. 



. 5. — Mars on the Evening of 1901 February 10, showing the Successive Impressions on which the annexed Plate is based. 



1898-1899. 1900-1901. 



CScrUen' Bolton.) (E. Atlkins.) 



Fig. 6.— The Cyclops-Cerberus Region of Mars from 1891 to 1901. 



along with the rotational displacement, it is perfectly 

 logical to infer that the a[)pearance, no matter how 

 simplified by distance and exiguity, and the laws of 

 delicate vision, rests on a substratum of objective reality. 

 And such is precisely the case of the Martian canals. 

 In a valuable paper written in Knowledge for 1894, 



in Fig. 5. It must also be borne in mind that, in spite of 

 the exiguity of the disc, the eye cannot see sharply, at a 



* The canals have come out too narrow on this picture. This is 

 due to the fact that their edges were so light on my original drawing that 

 they could not sufficieutly impress themselves on the reproduction. 



