122 SCIENCE PROGRESS 



Soon after the discovery of the disc of Mars, came the 

 announcement from Huygens that the disc possessed surface 

 features from observation of which he felt assured that, like 

 the earth, the planet rotated upon an axis. The marking which 

 revealed this fact is the now well-known dusky wedge called 

 the Syrtis Major. 



A little later increased telescopic power showed to the 

 old observers the white areas covering the poles of the planet 

 whose behaviour has turned out to be the master key to the 

 explanation of almost all the detail on the disc which subsequent 

 scrutiny has revealed. 



But space does not permit me to follow historically all the 

 steps by which we have acquired our present knowledge of 

 the planet. Sufficient has been said to show that it has ad- 

 vanced pari passu with the power of optical instruments. 



The investigators who preceded Schiaparelli laid the 

 foundations of areography, as the subject is named which 

 describes the configuration of the Martian surface features 

 — patches of colour, green and ochre, white and grey, which 

 cover the disc with their varied hues, making it appear like a 

 gigantic gleaming opal. On looking at Mars we perceive them 

 at once. Their outlines are well defined and have long since 

 been laid down in maps of the planet. 



The delineation of these features was well-nigh complete 

 when Schiaparelli began his studies of the planet in 1877. 

 The opportunity then afforded was an exceptionally favourable 

 one, the planet being very near the earth when showing the 

 fully illumined face of opposition. 



At this time the disc was so much dilated by its proximity 

 that with a magnifying power of only eighty diameters it 

 appeared in the telescope as big as that of the moon seen by 

 the unaided eye. Schiaparelli and the world alike were startled 

 on this occasion by the discovery of numerous dark lines criss- 

 crossing in the most unexpected fashion the ochre-coloured 

 regions of the planet. 



Following the well-worn analogy of his predecessors — oi 

 land and sea areas on the planet— he christened these new 

 features " canali " or channels, which reckless translators at once 

 dubbed canals, a name implying more than the astronomer had 

 actually found on the planet. 



At each subsequent opposition he succeeded in seeing them 



