NOTES ON MARS. 



The following article by Sir Robert Ball, which appeared as long ago 

 as 1893, is republished on account of its clear, untechnical statement 

 of a proposed theoretical means for determining if Mars has or has not 

 an atmosphere, which has been lately the subject of much discussion, 

 for, since it appeared, this interesting theory of Mr. Johnstone Stone}^ 

 has received different interpretations, and some of these are adverse 

 to the belief in a Martian atmosphere. 



It is, indeed, probable, from observation, that there is little atmos- 

 phere, or at least little like our own, and it is doubtful whether there is 

 water or snow, but observations are not consistent, and the question 

 must be considered as still debatable. The conclusions of Mr. Stoney, 

 are not, however, universally accepted. For instance, Mr. Cook, in 

 the Astrophysical Journal for January, 1900, using other assumptions, 

 comes to the conclusion that, although Stoney's result for the moon 

 may be true, that j^et the earth and the major planets might not only 

 retain an atmosphere of nitrogen and oxygen, but also of hydrogen 

 and helium. — S. P. L. 



I. Mars.' 



By Sir Robeet S. Ball, F. R. S. 



* * * From one cause or another it happens that Mars is the most 

 worldlike of all the other globes which come within the range of effective 

 observation. It would, indeed, be very rash to assert that other bodies 

 may not have a closer resemblance to our earth than Mars has, but of 

 them we have either little knowledge, as in the case of Venus, or no 

 knowledge at all. No doubt both Jupiter and Saturn can vie with Mars 

 in the copiousness of detail with which they delight the astronomers 

 who study them. These grand planets are deserving of every attention, 

 but then the interest they excite is of a wholl}'' different kind from that 

 which makes a view of Mars so attractive. Jupiter offers us a meteoro- 

 logical study of the most astounding cloud system in creation. Saturn 

 gives an illustration of a marvelous dynamical system, the like of which 

 would never have been thought possible had it not actually presented 



^ From Publications of the Astrononiical Society of the Pacific, January 28, 1893, 

 vol. 5, No. 28. Reprinted (with omissions) from Goldthwaite's Geographical Maga- 

 zine for December, 1892. 



157 



