THE PLANET MARS 129 



of both. Of this I may perhaps be permitted to quote an 

 instance. 



Searching for canals at Flagstaff during the opposition of 

 1909, using a yellow screen before the eye-piece and an aperture 

 of 18 in., I was amazed, on glancing off the disc to the sur- 

 rounding sky, to see a minute point of light, which turned 

 out to be one of the satellites. Lowell, when his attention 

 was drawn to it, perceived it also. Canals were visible to 

 him which I could not see and the satellite which had escaped 

 his notice was evident to me. 



There are many features visible on Mars which can only 

 be represented by drawings and to make these successfully 

 requires special qualifications of memory in the observer as 

 well as quick and acute vision. To be convinced on this 

 point it is only necessary to read the reports on the recent 

 eclipse of the sun, a phenomenon so fleeting as to serve our 

 purpose well. 



As many readers may remember, this eclipse was just total 

 on the central line in Portugal during perhaps a second, cer- 

 tainly not much more. I quote from an observer who was 

 very near this central line. Referring to the orientation of 

 the solar crescent in mid-eclipse he says : " In the excitement 

 of the moment I did not see whether the crescent of the sun 

 as it passed from the left to the right side of the moon passed 

 below or above it." Again he says : " As the event proved 

 we were too far south-east to be in the track of totality." 



It is certain from his position that the crescent did pass 

 on one side only of the lunar disc. Further it is clear that 

 the passage of the crescent must have been comparatively 

 slow, occupying at least a large fraction of a second. Also 

 the observer was not without experience, as he was observing 

 a total eclipse for the fourth time. It is therefore evident 

 that the omission which he so honestly admits was not one 

 of eyesight but of memory. 



As has been said, the best views of Martian detail seldom 

 last a second. The positioning of this detail is of the same 

 order of difficulty as the observation quoted. 



The next point which claims the attention of the observer 

 is his skill, which means command over the materials which 

 he uses. Many misconceptions of the appearance of Mars 



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