MAES, BY THE LATEST OBSERVATIONS, 187 

 MAES, BY THE LATEST OBSERVATIONS. 



FBOM THE FEENOH OF OAMILLE FLAMMAEION. 



IN" order successfully to observe Mars, two conditions are requisite : 

 First, the earth's atmosphere must be clear at the point of obser- 

 vation ; and, second, the atmosphere of Mars must be also free from 

 clouds — for that planet, like the earth itself, is surrounded by an 

 aerial atmosphere which from time to time is obscured by clouds just 

 like our own. These clouds, as they spread themselves out over the 

 continents and seas, form a white veil which either entirely or par- 

 tially conceals from us the face of the planet. Hence the observation 

 of Mars is not so easy a matter as it might at first appear. Then, 

 too, the purest and most transparent terrestrial atmosphere is com- 

 monly traversed by rivers of air, some warm, some cold, which flow 

 in different directions above our heads, so that it is almost impossible 

 to sketch a planet like Mars, the image seen in the telescope being 

 ever undulating, tremulous, and indistinct. I believe that, if we were 

 to reckon up all the hours during which a perfect observation could be 

 had of Mars, albeit his period of opposition occurs every two years, 

 and although telescopes were invented more than two and a half cen- 

 turies ago, the sum would not amount to more than one week of con- 

 stant observation. 



And yet, in spite of these unfavorable conditions, the Planet of 

 War is the best known of them all. The moon alone, owing to its 

 nearness to us, and the absence of atmosphere and clouds, has at- 

 tracted more particular and assiduous study; and the geography 

 (selenography 1 rather) of that satellite is now satisfactorily deter- 

 mined. That hemisphere of the moon which faces us is better known 

 than the earth itself; its vast desert plains have been surveyed to 

 within a few acres ; its mountains and craters have been measured to 

 within a few yards ; while on the earth's surface there are 30,000,000 

 square kilometres (sixty times the extent of France), upon which the 

 foot of man has never trod, which the eye of man has never seen. 

 But, after the moon, Mars is the best known to us of all the heavenly 

 bodies. No other planet can compare with him. Jupiter, which is the 

 largest, and Saturn the fullest of curious interest, are both far more im- 

 portant than Mars, and more easily observed in their ensemble, owing 

 to their size ; but they are enveloped with an atmosphere which is al- 

 ways laden with clouds, and hence we never see their face. Uranus and 

 Neptune are only bright points. Mercury is almost always eclipsed, 

 like a courtier, by the rays of the sun. Venus alone may compare 

 with Mars ; she is as large as the earth, and consequently has twice the 



1 Selene, the moon. 



