THE STRANGE MARKINGS ON MARS. 43 



increase the difference to such an extent that the seasonal changes 

 might be fatal to all higher forms of life. We have only to recol- 

 lect how powerful the effect of the comparatively moderate va- 

 riations between the seasons of our own planet is upon the human 

 organism in order to understand what must be the condition of 

 things in the southern hemisphere of Mars, where the passage 

 from one season to the other presents the succession of violent 

 winter cold, accompanied by days of gloom and faint sunshine, 

 followed by a blazing summer, with the sun hanging overhead, 

 visibly increased in apparent size by its approach. Telescopic 

 observations show clearly by the great variation in the extent of 

 the polar snows how extensive is the effect of these changes upon 

 the surface of the planet. In the hot summer the snows rapidly 

 retreat toward the pole, and even leave the actual pole itself bare 

 of snow, showing that upon Mars, as upon the Earth, the center, 

 or pole, of greatest cold (at least in the southern hemisphere) 

 does not coincide with the geographical pole of the planet. Then, 

 with the on-coming of winter, the march of the snows begins and 

 they rapidly advance further and further toward the equator, 

 spreading over the antarctic regions until another change of sea- 

 son brings back a flaming sun to melt them away. It should be 

 added that, as Prof. Young has remarked, the climate of Mars, 

 upon the whole, appears to be much milder than we should nat- 

 urally have expected in view of its distance from the sun. 



Bearing in mind these general facts about the size of Mars 

 and its position in the solar system, we shall now proceed to the 

 discussion of its surface phenomena as revealed by the telescope, 

 merely pausing to remark that the atmosphere of Mars is appar- 

 ently less dense than that of the Earth, and that the spectroscope 

 has demonstrated the presence of watery vapor in it. 



The little telescope of Galileo, which had enabled him to dis- 

 cover the phases of Venus, the satellites of Jupiter, the mountains 

 of the moon, the existence of Saturn's ring, and " vast crowds of 

 stars " in the Milky Way, was not powerful enough to show him 

 the markings that diversified the disk of Mars. The earliest draw- 

 ings of Mars that have come down to us were made by Fontana, 

 in Italy, in 1636 and 1638. They contain very little detail, the 

 best representing the planet simply with a darkish spot in the 

 center of the disk. Twenty odd years later Huygens made much 

 better drawings, and then the work was taken up by Cassini, 

 Maraldi, and others, with the cumbersome telescopes of the time, 

 the most powerful of which consisted of an object-glass suspended 

 high in the air by means of a long pole or other support, while 

 the eye-piece in the hand of the observer on the ground was, with 

 infinite difficulty, brought and kept in line with the optical axis 

 of the instrument. One of these telescopes was no less than three 



