MAES AND VENUS 317 



well be applied in this place. What purpose are the ca- 

 nals intended to subserve? Lowellians reply, "Irriga- 

 tion". If it can be shown, then, that there is cm ample 

 supply of clouds and moisture on Mars, the motive for 

 building the supposed canal system falls, and the whole 

 theory perishes with it. 



When the first edition of this work was in prepara- 

 tion (1911) I sought almost in vain for published testi- 

 mony supporting my deduction (from my theory of tidal 

 rotation) that Mars is plentifully supplied with oceans; 

 and though more of such testimony may have existed at 

 the time, all I could uncover was what is contained in this 

 paragraph, quoted from that edition: 



In one place in his book, Mr. Lowell graphically describes a 

 great Martian storm, in which the cloud was estimated by him to 

 be flying at a height of 14 miles above the planet's surface. He 

 expresses the opinion that this cloud was composed of sand, "be- 

 cause its color was almost that of the planet's surface," which, as 

 we already know, he assumes to be desert. Now if correspond- 

 ence of color between surface and cloud counts for anything, then 

 the cloud, according to my theory of a frozen-over ocean, should 

 have consisted of snow ; and the issue narrows as to whether sand 

 or snow is the likelier element to be found at an altitude of four- 

 teen miles in a case where the atmosphere is admittdly rare. 



Since that year, however, two oppositions of the 

 planet (which occur about two years apart) have taken 

 place, and it has been most carefully studied by a chain 

 of expert observers in various parts of the world led by 

 Prof. W. H. Pickering himself; and by him the results 

 have been elaborately reported, with photographs, in 

 Popular Astronomy, beginning with its January, 1914, 

 number. From these articles I cull only a small part of 

 a great wealth of material to the same effect: 



The clouds are sometimes so widespread and numerous, or 

 perhaps so thin, like our cirrus, as to partially conceal the detail 

 of a whole hemisphere. This was the case in 1894, and again at 

 one of the more recent oppositions. Photography shows (Har- 

 vard Annals 53, 167) that an equatorial belt of cloud is often 

 present, but this must be very thin, since it has not as yet been 

 observed visually. As regards color, it may be noted that our 

 own terrestrial clouds are by no means as white as snow. Some- 

 times when the sun is low and behind us, two clouds may be seen, 



