THE MYSTERY OF MARS — WILKINS 241 



It was stated that these sounds were not Morse and could not be 

 identified as coming from any station on this earth. They continued, 

 intermittently, for about three minutes. Nothing, however, came of 

 this, and it seems probable that the dots were a combination of atmos- 

 pherics and heterodyning or interference between various stations. In 

 1924 radio was in its early stages, and these signals almost certainly 

 had a terrestrial origin. Reports of the picking up of similar signals 

 were received from abroad; in America, for example, where it was 

 stated that they alternated between a long wave length of 25,000 

 meters and a short wave of 75 meters. 



At the previous opposition, in 1922, Professor Slipher at Flagstaff 

 had photographed a large white cloud which hung for four days over 

 the edge of the Pearl Bearing Gulf. 



A close approach took place in 1909, when Mars was observed by 

 Antoniadi and also by the French observer M. Jarry-Desloges. In 

 this year Syrtis Major had a pointed tip, while among the strange 

 changes noted were those in the canal Phison, which appeared double 

 on September 14 and 16, but single on September 15. It seems possible 

 that it was partly veiled by clouds on the latter date. The Lake of 

 the Sun was elongated in 1909, and a complicated system of canals 

 was seen to radiate from it. 



What appeared to be clouds projecting from the surface were seen 

 by Antoniadi on October 10, 11, and 12, 1924, while other clouds were 

 seen over Hellas. In 1924 most of the dark areas were very much 

 darker than usual, which suggests that the proximity of Mars to the 

 sun (it being summer in the southern hemisphere) may have favored 

 the development of vegetation. The polar cap soon showed dark rifts 

 within it, and began to break up into detached pieces which were 

 especially well seen on August 23. 



The opposition of 1926 was remarkable in many ways. It was not 

 so close an approach as that of 1924, but the planet was higher up in 

 the sky for northern observers. A special feature of this year was 

 the large number of clouds which were seen to distort the terminator 

 of the planet. Two such clouds were seen to the southwest of Syrtis 

 Major on September 15 by Antoniadi, while on December 15 at least 

 three such clouds were noted to the east of the Lake of the Sun or the 

 Eye of Mars. At times the whole planet seemed to have masses of 

 clouds or mists drifting over it, now hiding this and then that feature 

 on the surface. The canal Nepenthenes and Lacus Moeris, to the left 

 or west of Syrtis Major, were very broad and dark in this year, while 

 the Mare Tyrrhenum was clearly resolved into separate patches which 

 in all probability were more intensive areas of vegetation. 



A very large cloud apparently floating at a great height above the 

 surface was seen on March 16, 1929, by the same talented observer, 



