The Illumination of Venus’s Atmosphere at the beginning of her Transit across the Sun.
In Venus “the fatal gift of beauty” may be said, as far as our observations are concerned, to be matched by the equally fatal gift of brilliance. Whether it be due to atmospheric reflection alone or to the prevalence of clouds, Venus is so bright that considerable doubt exists as to the actual visibility of any permanent markings on her surface. The detailed representations of the disk of Venus by Mr. Percival Lowell, showing in some respects a resemblance to the stripings of Mars, can not yet be accepted as decisive. More experienced astronomers than Mr. Lowell have been unable to see at all things which he draws with a fearless and unhesitating pencil. That there are some shadowy features of the planet’s surface to be seen in favorable circumstances is probable, but the time for drawing a “map of Venus” has not yet come.
The previous work of Schiaparelli lends a certain degree of probability to Mr. Lowell’s observations on the rotation of Venus. This rotation, according to the original announcement of Schiaparelli, is probably performed in the same period as the revolution around the sun. In other words, Venus, if Schiaparelli and Lowell are right, always presents the same side to the sun, possessing, in consequence, a day hemisphere and a night hemisphere which never interchange places. This condition is so antagonistic to all our ideas of what constitutes habitability for a planet that one hesitates to accept it as proved, and almost hopes that it may turn out to have no real existence. Venus, as the twin of the earth in size, is a planet which the imagination, warmed by its sunny aspect, would fain people with intelligent beings a little fairer than ourselves; but how can such ideas be reconciled with the picture of a world one half of which is subjected to the merciless rays of a never-setting sun, while the other half is buried in the fearful gloom and icy chill of unending night?
Any amateur observer who wishes to test his eyesight and his telescope in the search of shades or markings on the disk of Venus by the aid of which the question of its rotation may finally be settled should do his work while the sun is still above the horizon. Schiaparelli adopted that plan years ago, and others have followed him with advantage. The diffused light of day serves to take off the glare which is so serious an obstacle to the successful observation of Venus when seen against a dark sky. Knowing the location of Venus in the sky, which can be ascertained from the Ephemeris, the observer can find it by day. If his telescope is not permanently mounted and provided with “circles” this may not prove an easy thing to do, yet a little perseverance and ingenuity will effect it. One way is to find, with a star chart, some star whose declination is the same, or very nearly the same, as that of Venus, and which crosses the meridian say twelve hours ahead of her. Then set the telescope upon that star, when it is on the meridian at night, and leave it there, and the next day, twelve hours after the star crossed the meridian, look into your telescope and you will see Venus, or, if not, a slight motion of the tube one way or another will bring her into view.
For many amateurs the phases of Venus will alone supply sufficient interest for telescopic observation. The changes in her form, from that of a round full moon when she is near superior conjunction to the gibbous, and finally the half-moon phase as she approaches her eastern elongation, followed by the gradually narrowing and lengthening crescent, until she becomes a mere silver sickle as she swings in between the sun and the earth, form a succession of delightful pictures for the eye.
Not very much can be said for Mercury as a telescopic object. The little planet presents phases like those of Venus, and, according to Schiaparelli and Lowell, it resembles Venus in its rotation, keeping always the same side to the sun. In fact, Schiaparelli’s discovery of this peculiarity in the case of Mercury preceded the similar discovery in the case of Venus. There are perceptible markings on Mercury which have reminded some astronomers of the appearance of the moon, and there are various reasons for thinking that the planet can not be a suitable abode for living beings, at least for beings resembling the inhabitants of the earth. Uranus and Neptune are too far away to present any attraction for amateur observation.
PROFESSOR WARD ON “NATURALISM AND AGNOSTICISM.”
By HERBERT SPENCER.
In a recent advertisement, Professor Ward’s work entitled as above was characterized as “one of the most important contributions to philosophy made in our time in England,” and this was joined with the prophecy that it “may even do something to restore to philosophy the prominent place it once occupied in English thought.” Along with laudatory expressions, I have observed in some notices reprobation of the manner adopted by Professor Ward in his attack upon my views—I might almost say upon me; and one of the reviewers gives examples of the words he uses—“ridiculous,” “absurd,” “blunder,” “nonsense,” “amazing fallacy,” “our oracle.”
When, some time ago, I glanced at one of the volumes, I came upon a passage which at once stamped the book by displaying the attitude of the writer; but, being then otherwise occupied, I decided not to disturb myself by reading more. Now, however, partly by the reviews I have seen, and partly by the comments of a friend, I have been shown that I can not let the book pass without remark. The assumption that a critic states rightly the doctrine he criticises is so generally made, that in the absence of proof to the contrary his criticisms are almost certain to be regarded as valid. And when the critic is a Cambridge Professor and an Honorary LL. D., the assumption will be thought fully warranted.