sought without the orbit of the former, and not between those of the two. Did it lie near the path of the remoter, it would still, if large, disturb that of the nearer also; while, if small, it would act upon the first only when in conjunction with it, or for a short time before and after that phase of nearest mutual approach; whereas the observed perturbations indicate an influence exerted during lengthened and continuous periods: therefore a large mass, located at a considerable distance from the one on which it acts, is to be looked for and estimated. But, if this distance exceed a certain determinate amount, the mass capable, at such a degree of removal, of disturbing to such an extent the motions of Uranus, will also reveal its presence by a smaller amount of disturbance on those of Saturn; therefore it lies within certain limits, both as regards distance and mass. Finally, these disturbances are in the plane of the orbit, not from it, either by ascent or descent; therefore the disturbing orb lies nearly in the same plane, and not greatly either above or below it. The way was thus so far clear; the approximative elements were thus rudely ascertained; and the rest was the work of patience, accuracy, zeal, and faith. And these labours ended in the discoverer's being able to give in minute detail the distance from the sun, the mass, the rate and period of revolution, and the inclination. of orbit, of the planet in question, before it had yet been looked for; and to indicate a very small zone of the heavens within which at one particular time it must be found.

The orb thus nobly discovered, is one which has for itself claims on our attention of the most imposing kind. It ranks the third of the secondary bodies of our system, its diameter being estimated at about 50,000 miles, and its mass at 230 times that of the Earth. Its distance from the sun is nearly 2,900,000,000 miles, or rather more than thirty times that of the earth; and the proportion of light and heat it receives from the central orb one nine hundredth () that which falls on our world. Its period of revolution round the sun is estimated at 172 of our years; and its mean rate of movement will therefore be little more than 10,000 miles an hour,-in strange contrast to that of the 'swift-winged Mercury,' which is 110,000. Whether or not it rotates upon its axis, is not yet definitely known, nor is it likely to be, unless some unwonted and peculiar phenomenon shall indicate the existence of such rotation, for years to come; and many other minor details with regard to the orb, the inclination of its axis, its possession of an atmosphere, &c., remain of course still to be investigated. One observer, Mr. Lassell, reports that he has seen what appears to him to be an attendant satellite; and likewise a peculiarity in the apparent form of the planet's

disc, which he refers to its being encompassed with a ring or rings like those of Saturn. The latter of these observations has since been confirmed by other astronomers: and we are thus presented with a second example of a phenomenon hitherto regarded as most singular; and the purpose of which the more sordid utilitarianism of our age is wholly baffled to define.

There are two facts, however, connected with the newly-discovered planet, the one certain, and the other all but certain, which merit particular attention. The first of these is its deviation to a far greater extent than any one of those bodies heretofore known, from what is known as Bode's law of the distances. According to this law-or rather rule, seeing it simply expresses a fact of which no explanation whatever can be given,-the various planets are placed at distances bearing a certain and uniform relation to each other: this proportion being that, the interval between Mercury and Venus being assumed as unity, the intervals between the successive orbs each double upon the one before it. Had the newly-discovered orb conformed to this rule, it would have been found at a distance of 3,600,000,000 miles from the sun. Its actual distance is about seven-ninths of this amount. And such a deviation, important and interesting in itself, as the first example of departure from a rule hitherto found universal, derives additional interest from the fact, that chiefly on it conjectures have already been founded relative to the possible existence of a second unknown orb, situated as much beyond the distance indicated by the law, as the present one falls within it. This conjecture, however, must be left to time to verify. It is more than probable that, if such an orb exist, the means which have guided our telescopes with such unerring aim toward this one, must again be employed for its discovery: its disturbing action be watched and waited for; and direct observation, almost powerless at such a distance, be guided and led out by theory toward a mind-seen result.

The second of the two facts we have referred to is one of yet higher interest and importance, and certainly one more unexpected still. It is believed that the planet is self-luminous. This inference has been deduced from its high degree of visibility and great clearness of light, not only as compared, or rather contrasted with Uranus, but beyond what is comprehensible in conformity with the known principles of optics. It is, indeed, conceivable, that the physical organisation of the orb may be such, as shall give to its surface a light-reflective power very far beyond all we have experience of, at least among the other orbs of the system; but it is very questionable whether any amount of this, within the limits of probability, would account for a

planet receiving little more than a third of the sunlight which Uranus receives, nearly equalling it in visibility, and far surpassing it in vividness of light. Here, too, at all events, we are called on to "stand still and see": to rid the mind of every bias, and of all prejudgment, and to esteem the treasure-house of physical variety still unexhausted, and the phases of physical appearance still not all seen. And should this most unexpected and important fact be hereafter established, we shall then be presented with a startling and striking converse to the fact arrived at by the masterly induction of the lamented Bessel, with regard to the stars Širius and Procyon-the first, one of the most majestic orbs which our firmament can claim,--that each is associated in binary combination with masses yet mightier than themselves, like our planets opaque and non-luminous; suns of darkness, whose light, if ever they shone, has waned and gone out for ever. And, on the supposition of the planet in question being self-luminous, it becomes an interesting object of inquiry whether, from any adjacent system, our sun can appear with it to constitute a double star. The same distinguished astronomer has succeeded not only in determining the distance from us, but in calculating very closely some of the elements, of a double star in the Swan, the only one with regard to which we have as yet definite estimate of the mass of the constituent orbs, and their distance from each other. According to him, the radius of their orbit is about three times that of Uranus, and the aggregate of their masses half that of the sun. Their separate masses cannot yet be determined; but they certainly far more nearly approach each other than do those of our primary orb and this his self-luminous attendant, and each is in revolution round their common centre of force, a phenomenon which cannot be presented by such a system as ours may exhibit. There are other cases, however, in which the two associated orbs are very much more disproportioned as to size-possibly as much so as our sun and his attendant; and in some at least of these, the apparent proximity of the orbs is much greater than that of the system investigated by Bessel. It is possible, then, that should the suspicion regarding Neptune be correct, our solar system may present itself to these as a double star, of which the smaller orb alone is in orbitual revolution; and possible, on the other hand, that some of those we see may be exactly analogous schemes. There are many of them, with regard to which double motion is still undemonstrated, and observation may yet reveal some in which it does not take place. Whenever such shall be made known to us, in which the larger orb is perfectly at rest with regard to the smaller, the probabilities will be very strong, that

in such a system the analogies with our own are yet more definite and extensive; and that a train of opaque planets, even as here, encircle at various distances, and with varying times, the primary orb. For it is due to the mutually counteracting and neutralising influence of these, that our sun exhibits no sensible revolution round their common centre of force; and were he alone with Neptune in the system, he would no longer hold his place of central repose.

The history of this beautiful discovery is, especially to the Englishman, in many respects a very painful record. Through the singular and obstinate faithlessness of an English astronomer-royal in mathematics generally, and specially it would seem in English mathematics and mathematicians, and his apparent ignorance of the true value and power of the tools which should have been very familiar to him; and the yet more extraordinary fact of a Cambridge professor of astronomy having again and again seen the object for which he was appointed to search, and was actually searching; seen it in the place where he was forewarned to expect it; seen it as a marked and conspicuous object; having on his own showing conducted his search for a new orb without a map of the stars at hand; having actually found that an orb not before seen had, in the interval between two examinations, wandered into the zone he was appointed to examine, without apparently a passing thought that this might be the one he was in search of;-by this unfortunate co-operation of singular faithlessness, and carelessness not often paralleled in the history of science, a young English mathematician has been deprived, to a great extent, of the honour of a discovery, which will deservedly immortalise the names connected with it; and with which too those of Mr. Airey and Professor Challis will, at least for a generation or two, be associated in a not very enviable notoriety. We say to a great extent; for the full right of independent, and at least simultaneous discovery, will by every ingenuous mind, French or English, be awarded to Mr. Adams: of that of prior public announcement, he has been, without fault of his, permanently deprived. The long standing and resolute faithlessness of the astronomer-royal has had its fitting meed of contempt rendered to it by the result; and we can well conceive it is with no very pleasurable feelings the Cambridge professor now knows

* In this class we do not include M. Arago, whose ingenuousness, at least where England and her science were concerned, has never been very brilliantly displayed. His dictum has already been pronounced,—that Mr. Adams has no right to be mentioned in connexion with the discovery. Unfortunately, however, for the realisation of this imperious judgment, the sway of M. Arago is limited, both as regards the present and the future; and it is quite possible that Mr. Adams's name may outlive his own.

that, within a very few hours of the communication to them of Le Verrier's last calculations,-as soon indeed as darkness permitted examination,-German eyes had seen what he might as easily have seen many months before. Our only regret with regard to Mr. Adams is, that the modesty natural to youth and obscurity prevented his at once publishing results, whose value they who were entrusted with them seem to have been so incapable of appreciating; when surely among all our British observers we might have hoped to have found one more wakeful, in eye and mind alike, than Professor Challis. But there are other circumstances still, which make the history of this discovery a painful one for the Englishman. We find from Mr. Airey's defensive statement itself, that the same faithlessness which has exercised so baneful an influence on the fame of Mr. Adams, has in all probability been the means of preventing the discovery being perfected ten years ago. In 1834, as we have already mentioned, the Rev. Mr. Hussey communicated to that gentleman his idea, that the irregularities of the path of Uranus were due to the perturbing influence of an unknown planet, revolving beyond that orb; and, backed by the coincident idea of M. Bouvard, who had previously been occupied in rectifying the theory of Uranus, requested the opinion of the English astronomer as to the possibility of investigating the suspected orb from these irregularities. The answer of the latter substantially was, that our mathematics were not adequate to such a task. In 1837, M. Bouvard again communicated with him on the subject; but his previous scepticism seems to have held out still. One reason-almost the only shadow of one, indeed-assigned by Mr. Airey for this scepticism is, that he did not conceive Bode's law of distance would be found to hold good beyond the orbit of Uranus; and that, therefore, it was vain to search in this way for an orb whose position in space was wholly unknown. We do not see what bearing Bode's law has on the matter at all. We presume neither of the two discoverers assumed it as holding certainly good with regard to the mass they were in search of: if they had, their labours would have been greatly increased, their results far less satisfactory, and probably the issue long postponed; for the body, as we have seen, deviates to a very considerable extent from that law. Indeed, the only relation we can discover between this conception or conjecture-for it was nothing more-and the inferences grounded on it, is one which seems to indicate that the mathematics of the English student and the French philosopher are of a higher order than those of Mr. Airey. The most elaborate problem he seems to have considered solvable is given a known result, and one of the elements of its causal origination,