amongst myriads of stars; just as the an- | Pouillet, estimating the specific heat of our nual revenue which enables an empire to luminary at 133 times that of water, infers fill every sea with its ships and every land with tokens of its power, would neither support a single pauper, nor make an appreciable addition to a rich man's pocketmoney, if equally distributed amongst its inhabitants.

of untoward weather intercepted their view of the sun. But, this passed, the apparition was not only found to have advanced some distance towards the western rim, but a smaller spot had emerged on the eastern border, and in a few days this was followed by a third. All were evidently in full march across the solar field, and all successively disappeared. Between the hope of seeing them again and the fear of losing them for ever, poor Fabricius was kept in a state of considerable agitation, and therefore it was with inconceivable pleasure that, after the lapse of some days, he saw the first of them spring up again on the eastern margin of the luminary. Then he knew, either that the objects in question must have made a complete revolution round the sun like little planets, or, that the sun itself, as Bruno and Kepler had suspected, possessed a rotatory motion of its own.

Now these spots have been the subject of much study in recent years, not only on account of their interest as solar eccentricities, but because it was expected that a correct understanding of their character would throw much light on the sun's constitution. Specks as they seem, their movements have been followed and their changes mapped down with an attention which might seem exaggerated if we looked upon them simply as a Lunarian might upon the clouds floating in our own atmosphere. In this country, Mr. Carrington, who published the results of his telescopic rambles in the spotted regions, in a splendid volume,* stands conspicuous; and Messrs. Warren de la Rue, Professor Balfour Stuart, and Mr. Loewy, who have devoted much time and thought to the same subject, have given (and the word must be taken in its literal sense) the fruits of their labours to the public in a series of valuable papers on Solar Physics.

measure towards the eye: in the centra! portions it is more fully displayed, because the object is travelling athwart the field of vision, whilst in receding, the conditions are reversed, and the pace appears, therefore, to be retarded. Then, too, it was observed, in studying the blots on the sun, that when there were several in sight, they generally took similar paths - tracing, as it were, parallel or concentric lines, like lines of latitude across his disc. Just so, we need scarcely say, the islands on our globe would appear to move in corresponding routes, the curvature being dependent upon the inclination of the pole to the plane of vision. Some specks there are, however, which seem to be endowed with a mobility of their own; for, unlike their island representatives here, they are occasionally observed to vary their distances from each other; one mentioned by M. Langier retreating from a neighbour at the rate of 111 metres per second. The proper motion of the spots, which follows a regular law of increase in proportion to their proximity to the equator, is found to be opposed in direction to that of the sun's rotation.

But these objects do not present themselves at random over the dazzling disc. They affect certain latitudes and eschew others. Even early observers of the phenomenon did not fail to notice that they rarely ventured out of a belt of 30 degrees on each side of the solar equator, which for that reason was designated the "royal zone." In a few instances, indeed, strag glers have been seen in much higher latitudes, and one very lonely and exceptional individual was discovered by La Hire as far north as 70 degrees. But, strange to say, they shun the equator itself almost as much as they do the polar circles. Out of 954 groups observed by Mr. Carrington, one If we imagine ourselves to be standing at only lay across the line; in four degrees on some distance from a terrestrial globe, and either side specimens were thinly scattered, regard the large islands which speckle the whilst in the belts comprehended between tropical seas as sun spots, we shall notice the 10th and 30th degrees (the northern changes of aspect due entirely to the rota- hemisphere, however, being more preferred tion of the sphere, if slowly and equably than the southern) they appeared with such performed. Take Madagascar, for exam-frequency, that it is obvious these must be ple. The island, on emerging from the regarded as their favourite promenades. "wooden horizon," would appear to move The most significant feature, however, somewhat tardily, but would proceed more rapidly as it approached the brass meridian;" this passed, it would slacken its pace gradually until it dipped into darkness on the other side. The reason is obvious. The motion, in the first place, is partly lost to us because the object is travelling in a

Observations of the Spots on the Sun, from Nov. 9, 1853, to March 24, 1861, made at Redhill, by Richard Christopher Carrington. 1863.

about these objects is their general con-
struction. They are not of uniform hue,
but in or towards the centre there is a dark
part called the umbra, or nucleus, and
round it there runs a greyish or more gently
shaded portion known as the penumbra, the
shape of the latter being dictated, in a great
measure, by that of the former, just as the
fringing round an island on
our artificial
globe adapts itself to the contour of the

island itself. This typical form, however, able. Follow one across the solar field, and admits of many variations, and is rarely after an interval of about 12 3-4 days realized in its perfect simplicity. There (during which the sun performs a semi-rev-. may be two or three or more black nuclei; olution) plus the advance made by the the penumbra may seem to be quite out of earth in its orbit, the same object will reapproportion to the central parts; the outlines pear modified in shape, but as near as may may be ragged and destitute of anything be identical in position. For six months a like true conformity; here we may have an big spot haunted the luminary in 1779, and eccentric specimen without any dark core, in 1840, Schwabe tracked another which reand there another which has dispensed en- turned not less than eight times. tirely with its shaded appendage. Not unfrequently the gloom of the black abyss in the centre (so imagination might deem it) is relieved by bright streaks or patches, and sometimes it is spanned by lines or arches of light, which Herschel happily described luminous bridges." Occasionally the penumbra has a striped or corrugated appearance, which has been compared, by another felicitous illustration, to the slopes surrounding a lake when furrowed by the beds of innumerable streams.

as

But passing over sundry other features in their character, there is one circumstance connected with the spots which is extremely important. It could not fail to be remarked that there were seasons in which they were abundant, and seasons in which they were scarce. Certain years have passed without a single speck being discovered, or at least recorded. By and by the question was asked, whether there could be anything periodic in their proceedings? Continuous study of their habits eventually showed that there was a regular cycle, and Herr Schwabe ascertained that for about five years they increased in number, whilst for about five years more they gradually declined. Wolf availing himself of still more extended observations, decided that this cycle occupied 11.11 years.

But whatever may be the shape the spot assumes, it undergoes certain changes, some of which are optical, and some internal. When first detected on the eastern border (telescopically viewed) the visitor looks like a line or a streak; as it advances it assumes an oval configuration; at the centre it attains its greatest rotundity, and then it A still more surprising coincidence was passes through reverse transformations be- detected. The intensity of the earth's magfore it runs off the opposite edge. Pre- netism, as expressed in the variations of cisely similar changes would appear in our the magnetic needle, is subject to a periodic Madagascar, making allowance for its increase and diminution. Curious to say, oblong contour, if surveyed from a distance this also is comprehended within a cycle of during a half revolution of the globe. The ten or eleven years; indeed, the two terms internal alterations are, of course, more appear to be nearly, if not wholly coincicapricious. The dark core may expand, dent. But does this correspondence in acbut usually the penumbra seems to invade tion imply connection in cause? One cirthe nucleus, and divide it into portions, or cumstance seems to point to such a concluoverflow it entirely, gradually vanishing it- sion. It is that the periods of maxima and self in turn. Occasionally patches break minima in the two cases are in exact acup with great rapidity, if we consider their cordance. It has been said, also, that prodigious bulk, for many of them are" magnetic storms occur with greater frevastly larger than our terrestrial continents; quency about every ten years, and at such several, indeed, having been upwards of seasons spots may be seen developing them50,000 miles across; and one of some selves in the sun, and changing their size notoriety mentioned by Dr. Wollaston, is and character with unusual rapidity, as if said to have shattered into fragments almost to show that the sympathy extended to the under the observer's eye.' * M. Flamma- most temporary fluctuations. rion gives a lively account of another which Again, it was suspected by the elder Herslowly threw off a smaller or infant spot by schel that the heat received from the sun was a process similar to that of fissiparous gen- greatest when the patches were most nueration: the parent left the little thing lag-merous; and, as some test of the accuracy ging in the rear, and sailed away composedly, whilst its offspring was agitated by internal movements and finally went down into the luminous sea around. The duration of some maculæ, however, is consider

Philosophical Transactions, vol. 64, p. 329. tComptes Rendus," vol. 67, p. 90.

of this surmise, he compared the price of wheat on our earth for a certain time previ ously with the state of affairs on the surface of the sun. Corn fell here (so he thought) as the spots rose there. Dr. Wolf also inferred from his observations that the driest and most prolific years on our planet coincided with those in which the sun's counte

nance had been most profusely speckled. |cently discussed this doctrine of planetary Arago, Barratt, and Gautier, however, have arrived at a contrary conclusion.

But this is not all. Other periods of variation have also been inferred, if not determined. Wolf discovered a large cycle of 55 years, a smaller epoch of 233 days, and then a tiny term of 27 days, which virtually synchronizes with the sun's rotation on its axis. Another of 584 days will presently be mentioned.

influence, and finds it necessary to insert the following proviso, namely, that a particular part of the solar surface should be considered more sensitive to foreign force than others. Granting this condition, he thinks it unquestionable that the sun-spots are ruled in their behaviour by the configurations of the nearer planets. To Mercury he ascribes the chief honour of managing the 11-year cycle; the 56-year period is due to the combined action of Mercury and the earth, whilst the 233-days' epoch is in significant accordance with the conjunctions of Venus and Jupiter.

Assuming the fact of periodicity then to be established in reference to the spots, we have to seek for some cause which operates with regularly varying power. Nothing can be more uniform in their play than the tides "We do not, of course,' say Messrs. De la upon our globe, but these heavings of the Rue, Stewart, and Loewy, "imagine that we ocean are due to a force from without. Can have as yet determined the nature of the influit be that the blemishes on the sun are the ence by these planets on the sun; but we would results of some external instead of some do- nevertheless, refer to an opinion expressed by mestic agency? Possibly the planets may Professor Tait, that the properties of a body, be the disturbers of its peace? De la Rue, especially those with respect to heat and light, Stewart, and Loewy have elaborately in- may be influenced by the neighbourhood of a vestigated this question, and indicated a large body.' Now an influence of this kind connection between the nearer planets and would naturally be most powerful upon a body the solar spots. Finding, from certain such as the sun, which possesses a very high data, that it was necessary to assume the temperature, just as a poker thrust into a hot furnace will create a greater disturbance of the existence of some travelling influence which heat than if thrust into a chamber very little returned to the same position with reference hotter than itself. In the next place, it is not to the earth in a period of about twenty to be inferred that the mechanical equivalent months, the mean being 584 days, Venus at of the energy exhibited in sun-spots is derived once stood detected. That was her synod- from the influencing planet, any more than it is ical time. Her bulk and proximity to the to be inferred that the energy of a cannon-ball sun would of course give her considerable is derived from the force with which the trigger power over Phoebus. Jupiter is more dis- is pulled.

tant, but his mass is very much larger, and The molecular state of the sun, just as that he, too, meddles with the solar affairs, of the cannon, or of fulminating powder, may though, not appparently, in a predominant be extremely sensitive to impressions from withfashion. Naturally enough, too, it might out; indeed, we have independent grounds for be expected that Mercury, diminutive as he from certain experiments, especially those of supposing that such is the case. We may infer is, would claim his share of influence in Cagniard de Latour, that at a very high temvirtue of his near relationship to the Head perature, and under a very great pressure, the of the system. Accordingly it was found, latent heat of vaporization is very small, so that that when Venus and Mercury were together a comparatively small increment of heat will in the heavens, there was evidence of a de- cause à considerable mass of liquid to assume cided excess of action, as compared with the the gaseous form, and vice versa. We may seasons when the two were estranged. It thus very well suppose that an extremely small was also ascertained that, when Venus, and withdrawal of heat from the sun might cause a probably Jupiter, crossed the solar equator, copious condensation, and this change of molecthe spots were drawn towards that region, ular state would, of course, by means of altered but when the planet attained its greatest reflection, &c., alter to a considerable extent the (heliographical) latitude, their tendency was distribution over the various particles of the to spread out in a polar direction. Could sun's surface of an enormous quantity of heat, these bodies act by intercepting the hail of and great mechanical changes might very easily meteors to which reference has been made, thus leaving blank or dark places where no fuel was supplied?

result."'*

What, then, do these spots indicate? According to some early theorists, they In a paper in the "American Philosophisuccess of this able and well-edited Journal, which cal Transactions," Dr. Kirkwood* has re-posts up the science of the day promptly, and promises to be of signal service both to students and savans.

*See a notice of Dr. Kirkwood's Paper in "NATURE," (13th January, 1870). We gladly seize this * "Researches on Solar Physics." Second Seopportunity of expressing our good wishes for theries, p. 45.

consist of smoke hovering in the sun's] the vapour in the form of steam, and that atmosphere, or of scum and scoriæ swim- its particles would affect that well-known ming at the surface of his ocean, like the spheroidal" state, in which attraction and refuse in a furnace of molten metal. In the repulsion are so critically adjusted; moreopinion of others, great volcanoes lay con- over, the existence of an ocean—a solar cealed at the bottom of the shining sea, and Atlantic-as the necessary source of this these, ever and anon, cast up masses of vapour, was also deemed practicable, seeing "bituminous matter," which appeared to us that the enormous pressure of the atmoas specks, but might be compared to tempo- sphere would keep the fluid from flying off rary islands, like that of Santorin, except unless heated far beyond our terrestrial that they wasted more rapidly away; whilst boiling-point. But vapour so formed must, others again imagined that the maculæ were sooner or later, descend. It would do so projecting parts of the solar globe left dry in the shape of rain, and, where a copious and exposed by the retreat or withdrawal downfall occurred, there spots might be of the luminous substance for the time, in supposed to appear. Since, however, consequence of a species of tidal action. recent spectroscopic research, as Janssen shows, seems to negative the existence of aqueous matter in the solar envelope, it would be premature to assert that our luminary is a place for simmering seas and scalding showers.

M.

- formed in the lower part of the atmosphere in consequence of some diminution of temperature in the underlying portions of the sun's surface. This cloud, intercepting the flow of heat from beneath, would lead to the production of another, more shadowy in its structure, at a much higher point in the envelope; the latter constituting the penumbra, the former the core of the spot.

Far more plausible, however, was the view propounded by Dr. Alexander Wilson, of Glasgow, about the year 1774. His idea was that spots were immense excavations in the body of the sun," some of them two, three or four thousand miles in depth, and On the other hand, Kirchhoff, who takes that the dark part was the floor of the hol- his stand upon a nucleus heated white hot, low, whilst the shaded portion represented intimates that a spot may be an agglomerits sloping sides. This conclusion was de-ation of gaseous matter - a chemical cloud duced from the fact that when an emergent specimen presented itself on the border of the disc, the further side of the penumbra was the first to become visible, then the nucleus, and afterwards the nearer side of the penumbra. On retiring from view these phases were reversed. There could scarcely be but one explanation. A funnel let into a sphere revolving under similar circumstances would exhibit similar results; a cone or projecting body certainly would not. In the theory as revised by Sir W. Herschel, the penumbra was attributed to a cloudy stratum in the sun's envelope, which reflected the light of the luminous stratum above, while the solid body of the orb, shaded by clouds, reflected little or none. And in some shape or another this notion that the spots are temporary rents or pits in the solar atmospheres has proved the most popular hypothesis of all. Unfortunately for Wilson's views, he held that the nucleus of the orb, visible through the chasm, was dark and cool, whereas that searcher of suns, the spectroscope, seems to point to the conclusion that it must be a ball of intensely heated matter.

So recently, however, as the year 1866, Professor Challis, writing on the subject of the solar atmosphere, suggested, that possibly the spots might, after all, be clouds of aqueous texture, in which case the coalescence of their globules would produce genuine raindrops. The obvious difficulty arising from the sun's elevated temperature was cleverly evaded, indeed utilized, by assuming that the excessive heat would raise

Dissatisfied with all previous solutions, M. Faye propounds another. The sun has no solid nucleus; it is gaseous to its centre. Owing to the heat garnered up in the interior, the forces of affinity and cohesion cannot operate freely there, but at the surface it is probable they will come into liberal play. Hence condensation, and afterwards precipitation, will ensue. A series of ascending and descending currents will be produced, the object being to transfer heat from the central reservoir of caloric to the radiating regions above. Where the upward currents prevail at the moment the luminous substance of the photosphere will be temporarily dispersed, and the observer looking down through the aperture thus produced, will see the gaseous core, dark and opaque to all appearance, not because it is cold, but because, even if heated to incandescence, its radiating faculties are too slight to render it visible when contrasted with the resplendent material by which it is surrounded.

Now, to say nothing of the inadequacy of this theory on various grounds-failing, as it does for instance, to meet the exigencies of perspective, for the nucleus should