THE PLANET VENUS.

New Zealand Times, Volume XXIX, Issue 4229, 9 October 1874, Page 3

THE PLANET VENUS.

The following observations on the beautiful planet, which is shining brilliantly in the western heavens every evening, are taken from Proctor’s “ Other Worlds than Ours,” one of the latest works on astronomy;— The peculiarities which characterise Venus are for the most part similar in kind to those we have had to consider in the case of Mercury. But at the outset of our inquiries into the physical habitudes of this most beautiful planet, we must point to the striking resemblance which it bears,, in some respects, to our own earth. So far, indeed, as telescopic and physical researches have yet led us, the planet Mars, as we shall, presently see, appears to exhibit habitudes more closely corresponding to those we are apt to consider essential to the wants of living creatures. But in size, situation, and in density, in the length of her seasons and of her rotation, in the figure of her orbit, and in the amount of light and heat she receives from the sun, Venus bears a more striking resemblance to the Earth than any orb within the solar system. In fact, there is no other pair of planets between which so many analogies can betraced as between Venus and the Earth. Uranus and Neptune are similar in many respects; but they differ in at least as many. Jupiter and Saturn are, in a sense, the brother giants of the solar scheme, while the dwai-f orbs, Mars and Mercury, present many striking points of similarity ; but between neither of these pairs can we trace so many features of resemblance as those which characterise the twin planets Venus and Terra, while the features of dissimilarity in either pair are perhaps even more obvious than the points of resemblance. Had Venus but a moon, as the earth has, we might doubt whether, in the whole universe, two orbits exist which are so strikingly similar, to each other. And here we may pause for a moment to consider one of the most perplexing enigmas that has ever been presented to astronomers. Are we indeed certain that Venus has no moon? The question seems a strange one, when it is remembered that year after year Venus has been examined by the most eminent modern observers, armed with telescopes of the most exquisite defining power, without any trace of a companion orb being noticed. Nor, indeed, can any reasonable doubts be entertained respecting the moonless condition of Venus, by those who appreciate the character of modern telescopic observations. And yet, if I had begun this paragraph by stating the evidence in favor of the existence of a-satellite, I believe that nearly every reader would have come to the conclusion that most certainly the Planet of Love has an attendant orb. They afe not amateur observers only who have seen a moon attending on Venus, but such astronomers as Cassini and Short, the latter with two different telescopes and four different eye-pieces. Pour times between the 3rd and 11th May, 1761, Montaigne saw a body near Venus, which presented a phase similar to that of the planet, precisely as a satellite would have done. Prom these observations M. Baudouin deduced for the new star a diameter of about 2000 miles, and a distance from Venus nearly equal to that which separates the moon from the earth. In March, 1761, again llodkier saw the enigmatical companion ; Horrebow saw it a few days later ; and Montbaren saw it in varying positions on the 15th, 28th, and 29th March. Lastly,- Scheuten, who witnessed the transit of Venus in 1761, declares that he saw a satellite accompany Venus across the face of the sun. So that we panUot be greatly surprised that even so skilful an observer as the late Admiral Smyth was-disposed- to believe in the existence of a satellite, of Vouus. “ The' contested satellite is, perhaps,”, he remarked, “ extremely minute, while some parts of its body may be less capable of reflecting light than others ; and when the splendour of its primary and our inconvenint station for watching it are considered, it must be conceded that, however slight the hope may be, the search ought not to be relinquished.” Venus lias a year of 221 days 17 hours, very nearly, and her distance from the sun, which varies little during the course of a year, is somewhat less than three-fourths of that which separates the sun from us. Her day is about thirty-five minutes shorter than ours, and her globe somewhat smaller than the Earth’s.

The arctic regions of Venus extend within 15deg. of her equator (if the axis is really bowed as supposed), while the tropics extend within 15deg. of her poles—so that two zones, larger by far than the temperate zones of our earth, belong both to her arctic and to her tropical regions. It is difficult to say whether her equatorial, her polar, or her artico-tropical regions would be, to our ideas,' the least pleasing portion of her globe. An inhabitant of the regions near either pole has to endure extremes of heat and cold, such as would suffice to destroy nearly every race of living beings subsisting upon the Earth. During the summer, the sun circles continually close to the point overhead, so that, day after day, he pours down his rays with an intensity of heat and of light exceeding nearly two-fold the midday light and heat of our own tropical sun. Only for a short time, in autumn and in spring, does the sun rise and set in these regions. A spring or autumn day, like one of our days at those seasons, lasts about twelve hours; but the sun attains at boon, in spring or autumn, a height of only a few degrees above the horizon. Then presently comes on the terrible winter, lasting about; three of our months, but far more striking in' its sharacteristics even than the long winter night of our polar regions. Eor, near our poles, the sun ’approaches the horizon at the hour corresponding to noon; and though he does not show his face, he yet lights up the southern' skies with a cheering twilight glow. ■ But during the greater part of the long night of Venus’s polar regions,' the sun does not Approach within many degrees of the horizon. Nay, Tie is farther below ttie horizon than the midnight winter ,sun. of our arctic regions., , Thus, Unless the'skies are lit,up with auroral splendours, an intense darkness, prevails during the polar , winter, which must add largely to the horrors,of that terrible season. Certainly, none of the human races upon our Earth. could bear the alternations between these more than polar terrors and an intensity of summer heat far I .exceeding any with, which we are familiar on earth.

Jjet us see whether the. equatorial regions are more pleasing abodes,. In these parts of Venus there aro two summers, corresponding to the spring and autumn of the polar regions. At these seasons, the sun rises day after day to , the point overhead, and the weather, corresponds for a, while, to .that which prevails.in the tropical regions of our own earth. But between these' seasons the,'sun passes away alternately to the northern and southern skies. During the season corresponding to summer, he is above the horizon, nearly throughout the twenty-three and a, quarter hours of Venus’s day ; ‘but ho attains no great elevation, travel-; ling always in a small, circle close around the northern pole. During the. season correspond-ing-to> winter, he is above the horizon only a very short time each day, and is always close to tho south, attaining, only an elevation of a few degrees-at. noon. . Thus we; have the following curious; succession of .seasons : —-A.t thevernal equinox a summer much warmer than our tropical ■ summers ;; about,. fifty-six .days later, or at the summer solstice, weather resembling : somewhat, thespring -of our temperate zones, only that the night is exceedingly short ; yet fifty-six days later there is another summer, as terrible ( as. the . former; and lastly, •at the winter solstice, the 1 days are shorter andithe cold probably more intense than in the Winter

* On the equator itself, as on our own, the day is always equal in length to the night. Tho above account corresponds to a place near the borders of the equatorial zoce

of places near our arctic circles. In such regions the contrasts, rather than either of the extremes of climate, would be most trying to terfestial races ; and it is scarcely too much to say, that no races subsisting upon our earth could possibly endure such remarkable changes, succeeding each other so rapidly. Lastly, the beings who inhabit the wide zones which are at once tropical and arctic have climates ranging between the two limits just considered. If they are near the equatorial regions they suffer from all the vicissitudes of the equatorial climate, with this further tribulation that in midwinter they do not see the sun even at mid-day—a circumstance by no means compensated (according to our ideas) by the fact that near the summer solstice the sun does not set. ■lf they are near the polar regions they have a summer even more terrible than the polar summer, and a winter scarcely less dreary and severe. Gravity at the surface of Venus is so nearly equal to terrestrial gravity that the difference is altogether insufficient to introduce any noteworthy effects. The delicate adjustment of the sap passages of plants to the force of terrestrial gravity, which Hr. Whewell notices in his “Bridgewater Treatise,” might indeed be disturbed if the earth’s gravity were suddenly made equal to that of Venus. But it would be strangely to limit our conception of nature’s powers of adaptation to suppose that therefore there can be no vegetation on Vefius resembling that with which we are familiar. Venus is the only planet the extent of whose atmosphere has been carefully estimated. If Venus had no atmosphere, she would present, when horned, a semicircular convexity ; whereas the refractory effects of an atmosphere, by causing the sun to illumine rather more than a full hemisphere, would tend to lengthen her horns. It. has been found that her convexity when she is horned exceeds a semicircle, and from the observed extent of this excess,, it has been calculated, that her atmosphere is so far more extensive than ours as to make its refractive effects on a body near the horizon about one-third greater. ' So that as this is about the proportion in .which the diameter of the sun as seen from Venus exceeds that which he presents to us, the inhabitant of Venus, like the inhabitant of our earth, sees the sun fully raised above the horizon at the moment when, but for refraction, his orb would be just concealed beneath it. Of the constitution of the atmosphere of Venus we know little. The spectrum of her light shows the dark lines which belong to the solar spectrum, and the Padre Secchi has noticed certain faint lines, which seem to indicate the presence of aqueous vapour in the atmosphere of the planet. But he scarcely gives satisfactory evidence that the lines he has thus seen were not due to the absorption exercised by aqueous vapour in our own atmosphere. The same observer finds, in the strengthening of the nitrogen lines near the E line of the spectrum, evidence that the atmosphere of Venus is constituated very similarly to the air we breathe.

On the whole, the evidence we have points very, strongly to Venus as the abode of living creatures not unlike the inhabitants of earth. With the sole exception of the inclination which has been, without sufficient evidence, assigned to the planet’s equator, I can see nothing which can reasonably be held to point to an opposite conclusion. Certainly the strong light which the sun pours upon Venus need least of all be objected to, since, if there is one adaptative power which Nature exhibits more clearly than another, it is that by which the various creatures we are acquainted with are enabled to live in comfort under all degrees of light, from the obscurity in which the mole pursues his subterranean researches to the blazing light of the noon-day sun towards which (in fable, if not in fact) the eagle turns his unshrinking eyes.