8+ THE POPULAR SCIENCE MONTHLY. 



existence of such a body tliat we have not yet seen it ; but it ought 

 to serve as an argument to stimulate us to apply our most powerful 

 instruments to the regions around this planet with more frequency and 

 attention than we have hitherto done, and it is possible that our dili- 

 gence may be rewarded with the discovery. The long duration of 

 winter in the polar regions of Mars seems to require a moon to cheer 

 them during the long absence of the sun ; and, if there be none, the 

 inhabitants of those regions must be in a far more dreary condition 

 than the Laplanders and Greenlanders of our globe." 



This state of doubt and uncertainty in relation to the question of 

 the existence of Martial moons afforded legitimate game for the satiri- 

 cal writers of the last century. Thus, Jonathan Swift, in his " Gulli- 

 ver's Travels," published about 1727, in giving an account of the ex- 

 traordinary race of abstract philosophers who inhabited the " Floating 

 Island " called Laputa, informs us that " they spend the greater part 

 of their lives in observing the celestial bodies, which they do by the 

 assistance of glasses far excelling ours in goodness ; for, although their 

 largest telescopes do not exceed three feet, they magnify much more 

 than those of one hundred with us, and show the stars with greater 

 clearness. This advantage has enabled them to extend their discov- 

 eries much farther than our astronomers in Europe ; for they have 

 made a catalogue of 10,000 fixed stars, whereas the largest of ours 

 does not contain above one third of that number. They have likewise 

 discovered two lesser stars or satellites, which revolve about Mars ; 

 whereof the innermost is distant from the center of the primary planet 

 exactly three of its diameters, and the outermost five ; the former re- 

 volves in the space of ten hours, and the latter in twenty-one and a half; 

 so that the squares of their periodical times are very near in the same 

 proportion with the cubes of their distances from the center of Mars ; 

 which evidently shows them to be governed by the same law of gravi- 

 tation that influences the other heavenly bodies." 



About twenty-five years after Swift wrote the foregoing, that is in 

 1752, the celebrated Voltaire (apparently in imitation of " Gulliver's 

 Travels ") cuttingly ridicules the pretensions of the class of reasoners 

 who found their conclusions upon analogy. In one of his satirical 

 tales, Micromegas, an imaginary inhabitant of Sirius, is supposed to 

 make a voyage of discovery through the solar system in company with 

 a denizen of Saturn ; they philosophize as they go. Approaching the 

 planet Mars, Micromegas and his companion plainly descried two 

 moons acting as satellites to that body — moons which have certainly 

 escaped the ken of terrestrial astronomers. " I know perfectly well," 

 continues the author of the tale, "that Father Castel" (an astronomer 

 of the time) " will write, and write sufliciently pleasantly, too, against 

 the existence of these two moons ; but I appeal against his decision to 

 logicians, who reason from analogy. These excellent philosophers are 

 perfectly aware how difficult it would be for Mars — a planet so far re- 



