ral powerful telescopes; and he was able to recognize distinct inequalities in the boundary. These irregularities varied in figure from time to time, precisely as they might be expected to do when we consider their cause. Now a plain or sea, now a high table-land would be at some particular part of this border-land between light and darkness; now valleys, now mountain peaks would diversify the seeming figure of the boundary. Some of the effects recognized by Schröter were so remarkable as to suggest that the mountains on Venus must be very much higher than those on our earth. Schröter, indeed, estimated the height of some of these mountains at no less than twentyeight miles, or fully four times the height of the loftiest peaks on our own earth. A circumstance of some interest may be here touched upon in connection with the researches of Schröter. Sir William Herschel, having failed with his more powerful telescopic means, in detecting any of the appearances recorded by Schröter, wrote a somewhate lively criticism upon Schröter's statement. Of this paper, which appeared in the "Philosophical Transactions" for 1793, Arago remarked that it was "une critique fort vive, et, en apparence du moins, quelque peu passionnée." It must be said, however, in justice to the greatest telescopist who has ever lived, that the severity of his tone, though not justified by the actual circumstances, was by no means unwarranted by the facts as he saw them. Misapprehension not injustice led to the warmth of his tone. Schröter answered dispassionately and effectively in 1795; and no doubt now remains of the general accuracy of the German astronomer's observations. The irregularities, whose effects thus show themselves by notching or otherwise distorting the boundary between the light and dark portions of the disc of Venus, have been detected also as faint spots within the illuminated portion of the disc. It is only, however, with great difficulty, and under exceedingly favorable circumstances, that they can be seen. And, singularly enough, it would by no means appear as though the most powerful telescopes, or even the greatest observing skill, were the necessary conditions for the detection of these spots. On the contrary, they have been seen with small telescopes when large ones failed to show them; and comparatively inferior observers, like Bianchini and De Vico, have recognized them, when Sir William Herschel and the eagle-eyed Dawes have been unable to detect any traces of their existence. Indeed, all that Sir William Herschel could detect was a slight superiority of brightness in the part of the disc near the edge as compared with the part close by the boundary-line between the bright and dark portions. This peculiarity he misinterpreted strangely; for he ascribed it to the existence of an atmosphere in Venus, failing to notice that it is clearly recognizable in the airless moon. The spots in Venus are not seen distinctly enough to enable us to judge whether they indicate the existence of land and water, like the greenish and the ruddy markings on Mars. But they have enabled astronomers to measure the rate at which Venus turns upon her axis, and they have also shown us how her axis is placed, so that we can form an opinion as to the nature of her seasons. Cassini was the first to time the rotation of Venus. He found that a certain spot returned to the same place on her face at intervals of about 23 hours, so that the length of the day in Venus would be slightly less than that of our own day. But Bianchini, in 1726, came to a very different, and a very startling, conclusion. He said he could not account for all the changes of appearance he had noted in Venus, without assigning to her a rotation period of 24 days and about 8 hours. Cassini had not been certain about his results, because he could not follow the spot far across the face of Venus. Bianchini's results were open to a somewhat similar objection. His observatory had not suf ficient sky-room to enable him to follow the planet for more than about 3 hours. Now he was convinced that the spots did not appreciably change their place in that time; and having made his observations at somewhat wide intervals, and finding that at the end of several days a spot seemed considerably advanced when observed at the same hour of the night, he concluded that all those days had been occupied in the advance alone. Cassini had judged that each day there was a circuit and a slight advance as well. That excellent astronomer, Ferguson, whose book (out of date as it is) continues far better worth studying than nine-tenths of our modern elementary treatises on astronomy, adopted Bianchini's explanation as seeming to accord best with the evidence. Working out the consequences after his usual sound and laborious fashion, he came to some very strange conclusions respecting the seasonal changes in Venus. Bianchini had seen reason to believe that Venus turns on an axis very much tilted down towards the level of her path round the sun; and the effects of this tilt would be very striking, even though the day of Venus were judged to be equal, or nearly so, to our own. But with the long day of 24 terrestrial days, the result ing effects were found by Ferguson to be so strange that nothing we are familiar with on earth could be very well compared with them. In the first place (according always to Bianchini's estimate) there are but 94 days in the year of Venus.* "We may suppose," says Ferguson, "that the inhabi *In my "Other Worlds" there is a note referring to a remark in Admiral Smyth's "Celestial Cycle," which had gravely perplexed me. For the Admiral says that in the year of Venus there are but 9 of her days, "reckoned by the sun's rising and setting, owing to which the sun must appear to pass through a whole sign in little more than three-quarters of her natural day." In the note referred to, I remark on this, "he gives no reason for this remarkable statement, which most certainly is not correct." I might well, indeed, be perplexed, not only by this particular statement, but by the whole of the Admiral's treatment of the seasonal and diurnal changes in Venus. For though he nowhere adopts Bianchini's estimate of Venus's rotation-period (on the contrary, he remarks that Schröter's researches have established Cassini's value), yet none of his statements are just if Venus turns round in about 24 hours. I have recently found that all Admiral Symth's remarks on the seasonal and diurnal changes in Venus were founded on Ferguson's examination of the matter. So that their incongruity is at once accounted for. But it is worthy of notice how important it is that no statement-however eminent its authority should be repeated without due examination, or failing that (as may well happen when a subject is very recondite), a careful reference to the source whence the statement has been drawn. Admiral Smyth doubtless thought that so accurate a mathematician as Ferguson could not go wrong, and so, neglecting inquiry, failed to notice that he was himself misinterpreting Ferguson. On the other hand, I was somewhat sharply censured for questioning the dicta of so sound a mathematician as the esteemed Admiral; yet it is now shown how necessary such questioning was in that instance. But in truth it is always so. Doubt in such matters ought to be held as an almost sacred duty by the scientific author. tants of Venus will be always careful to add a day to some particular part of every fourth year, by means of which intercalary day every fourth year will be a leap-year, and will bring her time to an even reckoning, and keep her calendar always right." Then the day lasting so long, the sun's mid-day height would be very different on successive days; so that if at any place he were overhead at noon on one day, he would be found far removed from the point overhead at noon of the next day. "This appears to be providentially ordered," says Ferguson, "for preventing the too great effects of the sun's heat (which is twice as great on Venus as on the earth); so that he cannot shine perpendicularly on the same places for two days together; and on that account the heated places have time to cool." One would have thought the long night of 292 hours would fairly have sufficed for this desirable purpose; but in Ferguson's day men knew more about the final causes of things than we do in our time, so that it is only with extreme diffidence that I venture this suggestion. When Ferguson wrote, the astronomers of England were paying great attention to the problem of finding a ship's longitude at sea. Ferguson points out how much better off the people in Venus are as respects their means of dealing with this problem. "The sun's altitude at noon being very different at places in the same latitude, according to their different longitudes, it will be almost as easy to find the longitude on Venus, as it is for us to find the latitude on our earth, which is an advantage we can never have." Here is another instance of an easily interpretable design. For our seamen have the moon to help them in finding the longitude; and the voyagers over Venus would be badly off without a moon but for the peculiarity pointed out by Ferguson. But it is as well, before inquiring what purpose was intended to be fulfilled by certain relations, to assure ourselves that those relations actually exist. For example, before asking why the people in Jupiter and Saturn get so much more moonlight from their many moons than we do from our single one, it is as well to calculate how much light they do actually get; because the argument from design is slightly interfered with when the multiple moonlight in Saturn and Jupiter is found to amount in all to scarce a twentieth of that which our single moon supplies to us. So here, in the case of Venus, it is unpleasing, after calculating all the important advantages afforded by the long day of Venus, to discover that the day in Venus is actually rather less than on our own earth. This, however, has now been abundantly proved. Schröter, by carefully noting the interval which elapsed between the successive appearances of a certain bright spot close by the southern horn of the crescent Venus, assigned a rotation-period of 23 days 21 minutes and 8 seconds. This was within a minute of the time which had been assigned by the younger Cassini as bringing his father's observations into agreement with Bianchini's. But the Italian observer, De Vico, attacked the question still more earnestly. He and several colleagues studied Venus at the Observatory of the Collegio Romano. They rediscovered Bianchini's spots, and by carefully comparing their own estimate of the planet's rotation with the observed appearance of Venus at such and such hours as recorded by Bianchini, they were able to deduce a very close approximation to the rotation-period of Venus. They assigned as the actual length of the day in Venus 23 hours 21 minutes 23 seconds and 93 hundredth parts of a second. Without accepting these hundredths as altogether beyond dispute, we may take 23 hours 21 minutes and 24 seconds as doubtless very closely representing the value of Venus's rotation period. Here, then, we have a day closely corresponding to that of our own earth, and also to that of Mars. In fact, the day of Venus falls short of our earth's day by about as much as the day of Mars exceeds our earth's. Instead of the year of 9 of her own days assigned to Venus by Bianchini, we find that she has a year of about 230 days. There is little reason then, thus far, for supposing that the seasonal and diurnal changes in Venus differ importantly from those on our own earth. But undoubtedly when we inquire into other circumstances on which the seasons and general climate of a planet must depend, we find some difficulty in regarding Venus as likely to be a quite agreeable abode for creatures constituted like ourselves. Before discussing these relations, however, let me as an anticipatory cor rective present the enthusiastic description which Flammarion has given of that which he can have seen only with his mind's eye, and that eye gifted with exceptional, and possibly deceptive, powers. "Some illdisposed minds," he says, as translated—. most pleasingly-by Mrs. Lockyer, "have asserted that although Venus is beautiful afar, it is frightful on a nearer view. I fancy I see my young and amiable readers; and I am sure that not one amongst them is of this opinion. Indeed, all the magnificence of light and day which we enjoy on the earth, Venus possesses in a higher degree. Like our globe, it is surrounded by a transparent atmosphere, in the midst of which are combined thousands and thousands of shades of light. Clouds rise from the stormy ocean, and transport into the sky snowy, silvery, golden, and purple tints. At morning and evening, when the dazzling orb of day, twice as large as it appears from the earth, lifts its enormous disc at the east, or inclines towards the west, the twilight unfolds its splendors and charms." This is very pleasant to contemplate; but it is desirable to inquire how far it is warranted by known facts. I To begin with the excessive light and heat which the sun pours upon Venus. suppose no one doubts that quite possibly this great light and heat may be so tempered as to be not only endurable, but pleasant to people in Venus. But so far as terrestrial experience is concerned, we are assuredly not justified in saying that this must be so. Undoubtedly, if the sun began suddenly to pour twice as much light and heat upon the earth as he actually does, the human race would be destroyed in a very few months. In tropical regions the destruction would be completed in a single day. In temperate regions the beginning of the first summer would be fatal. Nor would the denizens of arctic and subarctic regions live through the heat of a midsummer's nightless day. Suppose, now, we assume that the atmosphere of Venus, as good observers. have judged, is considerably deeper than our own. This we may fairly do, because certainly the estimate of observers would be more likely to fall short of the truth than to pass beyond it; so that, when trustworthy astronomers say that they have seen the twilight zone of Venus extending farther than we know our own does, we may fairly conclude that at a nearer view a yet greater extension of this sunlight atmosphere-for such is the real nature of the source of twilight-would be greater yet. Here, again, all that we know of the effects of a deep atmosphere would lead us to believe that the heat in Venus must be intensified by the action of her deep and dense atmosphere. As a matter of fact, it may not be so. All I urge is, that, judging from the only analogy we have to guide us, the depth and density of the atmosphere of Venus seem to promise no relief from the intense solar heat to which she is exposed. But it is when we consider the effects of her axial slope that we find the most urgent reasons for questioning how far life would be comfortable to ourselves in that beautiful planet which now adorns our twilight skies. In Bianchini believed in an amount of axial tilt (a tilt of the axis, that is, from uprightness to the path of Venus) which has not been confirmed by De Vico and his colleagues. Still their observations agree in assigning an axial tilt much more than twice as great as the earth's. other words, the arctic regions in Venus extend more than twice as far from her poles as ours do, and her tropical regions extend more than twice as far as ours from the equator. But we have only to take a terrestrial globe to see that, if we extend more than doubly the range of the tropics and of the arctic regions, these regions will overlap. There will be no temperate zone at all. Instead of it, there will be a region which is both tropical and arctic. Now, when we remember what is meant when we speak of a region as tropical or arctic, the significance of this statement will be recognized. At a place within the tropics the sun is always twice in each year immediately overhead at noon. At a place within the arctic regions there is always one period in the year when the sun does not rise, and another period when he does not set, all through the twenty-four hours. Conceive, then, first, the vicissitudes within the zone which is both arctic and tropical. Here we have, at one season, an arctic night—no sun shining all through the twenty-four hours; at another, an arctic day-the sun not setting during all those hours. Between these seasons, but nearer to the latter, we have two sea sons, when the sun is overhead at noon. The contrast between the bitterness of a season when the sun does not show at all, and the fiercely scorching heat of seasons when either the great sun of Venus does not set, or shines vertically down at noon upon such beings as may be able to endure his fury, is certainly not a pleasant prospect for terrestrial beings to contemplate. The young lady whom Flammarion lauds because she promised "swiftly to soar to Venus" when her "imprison'd soul was free," would have been justified in declining the visit on the score of expediency, while still encumbered with a body. And if "now," as Flammarion suggests, "she resides in that isle of light, and contemplates thence the earthly abode which she not long ago inhabited, perhaps she hears," not without amusement, "the prayers of those who, as she did formerly, allow their hopes to mount sometimes" to those pleasant-looking regions. Nor are the tropical or arctic regions more likely to be comfortable abodes for creatures constituted like ourselves. The seasonal contrasts and vicissitudes in these regions are always very marked, and recur much more rapidly than on our own earth. If the arctic regions are worse off in having a more marked difference be tween the greatest cold of winter, the tropical regions are worse off in having two summers and two winters within the short year of two hundred and twentyseven terrestrial days. I cannot but think that on a fair examination of the physical habitudes of Venus, we are led rather to Whewell's than to Brewster's opinion; though I am by no means ready to admit that either one or the other opinion is strictly sound. It is but barely possible, if possible at all, that Venus may be a suitable abode for creatures like ourselves and our fellow-inhabitants of this terrestrial globe. But we have no sufficient reasons for believing with Whewell that creatures so constituted as to exist in comfort in Venus must needs be wholly inferior to those which inhabit the earth. One word on the celestial scenery visible from Venus. It is a circumstance worth noticing that, from all the three planets which have no moons, at least one orb can be so seen as to appear more beautiful than any star or planet in our own skies. Jupiter, as seen from Mars, must appear a most noble orb, since his splendor, owing to the greater proximity of Mars (when most favorably situated for observing Jupiter), must be one half greater than that which he displays to ourselves. His satellites, too, may probably be visible from Mars. In the planet Venus, again, Mercury has a noble spectacle. Her lustre, indeed when seen under the most favorable circumstances, must illuminate the skies of Mercury with a splendor surpassing ten or twelve times that of the planet Jupiter as we see him on a midnight sky. From Mercury also the earth must seem a noble orb, her attendant moon being probably distinctly visible. Venus has not, like Mercury, a view of two planets surpassing Jupiter in splendor. But, on the other hand, the earth as seen from Venus must be the most beautiful spectacle visible throughout the whole range of the solar system. To vision such as ours the earth must present the figure of a disc, because we know that under favorable circumstances we can ourselves recognize the crescent form of Venus with the unaided eye. This disc cannot fail to exhibit varying colors; now appearing greenish, now reddish, according as the terrestrial seas or oceans are more fully turned towards Venus; while at times, when the atmosphere of our earth is heavily laden with vapors, the glory of the earth as a light in the skies of Venus must be greatly enhanced, the earth's lustre being at such times, however, purely white. In the meantime the moon must be distinctly visible, as a disc about one-fourth as large as the earth's in diameter, and not changing in color, as hers does, unless indeed it chan ces that the side of the moon we do not see differs very much in character from the portion we are able to study.* The seeming distance separating the moon from the earth when they are farthest apart will be somewhat greater than the seeming diameter of the moon as we see her. It need hardly be said that the light actually received from the earth and moon under these circumstances must be very much greater than that which we receive either from Jupiter or Venus when at their brightest. We know that Mars, when seen under most favorable circumstances (once in about a century), is fairly comparable with Jupiter; but at such times Mars is half as far again from us as we are from Venus; he would show a disc much less than half the earth's if both were seen at the same distance; and he is illuminated less than one-half as brightly, owing to greater distance from the sun. On all these accounts the earth must shine many times more splendidly than Mars does, even on those exceptional occasions when (as once during the last century) his ruddy orb blazes so resplendently as to be mistaken for a new star. When it is remembered, too, that Venus is seen most brightly when by no means at her nearest, and when showing less than a half disc, whereas the earth is seen most favorably from Venus when at her nearest, and showing a full disc, it will be seen that the greater intrinsic lustre of Venus is much more than counterbalanced, and that the earth with her companion moon, as seen from the planet Venus, must form a far more glorious spectacle (besides appearing on a far darker sky) than the Planet of Love when most she solicits our admiration. RICHARD A. PROCTOR. Macmillan's Magazine. PLEASANT RECOLLECTIONS OF FIFTY YEARS' RESIDENCE IN IRELAND. BY JOHN HAMILTON OF ST. ERNAN'S. I. MORE THAN HONEST. THE character of my fellow-countrymen is too much judged of from those details which most commonly meet the public eve, which for the greater part are pictures of the worst part of the Irish population, and, when not portraying crime and violence, represent the Irish man as a ridiculous, improvident, blundering booby. No doubt we have too many criminals, and a sufficiency of folly among us; but I am sure we have, notwithstanding many *The actual amount of light received from the earth and moon together, as seen from Venus, probably amounts to nearly the five-hundredth part of that which we receive from the moon at full. |