dazzling than that which Venus sends to us, both because, at our greater distance, the sunlight is less intense, and because our rarer atmosphere reflects a smaller proportion of the rays incident upon it.  But the earth is, after all, a more brilliant phenomenon seen from Venus than the latter is seen from the earth, for the reason that the entire illuminated disk of the earth is presented toward our sister planet when the two are at their nearest point of approach, whereas, at that time, the larger part of the surface of Venus that is turned earthward has no illumination, while the illuminated portion is a mere crescent.

Owing, again, to the comparative rarity of the terrestrial atmosphere, it is probable that the inhabitants of Venus—­assuming their existence—­enjoy a superb view of the continents, oceans, polar snows, and passing clouds that color and variegate the face of the earth.  Our astronomers can study the full disk of Venus only when she is at her greatest distance, and on the opposite side of the sun from us, where she is half concealed in the glare.  The astronomers of Venus, on the other hand, can study the earth under the most favorable conditions of observation—­that is to say, when it is nearest to them and when, being in opposition to the sun, its whole disk is fully illuminated.  In fact, there is no planet in the entire system which enjoys an outlook toward a sister world comparable with that which Venus enjoys with regard to the earth.  If there be astronomers upon Venus, armed with telescopes, it is safe to guess that they possess a knowledge of the surface of the earth far exceeding in minuteness and accuracy the knowledge that we possess of the features of any heavenly body except the moon.  They must long ago have been able to form definite conclusions concerning the meteorology and the probable habitability of our planet.

It certainly tends to increase our interest in Venus when, granting that she is inhabited, we reflect upon the penetrating scrutiny of which the earth may be the object whenever Venus—­as happens once every 584 days—­passes between us and the sun.  The spectacle of our great planet, glowing in its fullest splendor in the midnight sky, pied and streaked with water, land, cloud, and snow, is one that might well excite among the astronomers of another world, so fortunately placed to observe it, an interest even greater than that which the recurrence of total solar eclipses occasions upon the earth.  For the inhabitants of Venus the study of the earth must be the most absorbing branch of observational astronomy, and the subject, we may imagine, of numberless volumes of learned memoirs, far exceeding in the definiteness of their conclusions the books that we have written about the physical characteristics of other members of the solar system.  And, if we are to look for attempts on the part of the inhabitants of other worlds to communicate with us by signals across the ether, it would certainly seem that Venus is the most likely source of such efforts, for from no other planet can those features of the earth that give evidence of its habitability be so clearly discerned.  Of one thing it would seem we may be certain:  if Venus has intellectual inhabitants they possess far more convincing evidence of our existence than we are likely ever to have of theirs.