We miss accordingly a class of observations, which, had the shower been more confidently expected, would certainly have been suggested, we refer to prearranged comparison-observations. If observers separated by suitable distances, had assigned themselves the task of recording the phenomena presented by the first characteristic meteor appearing after certain definite epochs, we could not have failed to have satisfactory evidence respecting the average height and velocity of the shooting stars which composed the shower. The display loses half its significance for the want of this sort of evidence. Professor Challis justly remarks on the improbability that (without some such arrangement as we have suggested) single meteors could be observed "in different localities;" he adds, with apparent regret that so favourable an opportunity was allowed to pass unused, "it now appears to me that this class of observations is of great importance with respect to the theory of the phenomenon.'

The determination of the "radiant point" of the shower was effected, however, in a most complete and satisfactory manner. It will be remembered that in Humboldt's Cosmos,' some doubt is expressed as to Leo being the true constellation-radiant of the November shower. The accompanying Figure will show that

doubt can no longer exist on this point. It represents "the sickle" in Leo, within which group it had been announced that the radiant point might be looked for The evidence for the determination of this point was of a twofold character:-First, in the immediate neighbour

VOL. IV.

Q

hood of the radiant point the paths of meteors, being foreshortened, would be reduced to mere points; secondly, the paths of all the meteors produced backwards would indicate by their common intersection near a single point the existence and position of the radiant centre. Most of our best observers obtained satisfactory evidence of both sorts; all recognized the latter phenomenon. In the figure the results of nine sets of observations have been recorded:-The small cross marked (1) indicates the radiant point determined by Mr. Alexander Herschel; (2) we have deduced from the map of the Greenwich observers; (3) marks two crosses-the upper Mr. Hind's, the lower Sir J. Herschel's determination; (4) is Mr. Pritchard's; (5) Professor Grant's; (6) Professor Adams's; (7) marks two crosses the upper Professor Challis's determination, the lower Mr. Baxendell's. Mr. Herschel quotes ten other results, some of which we have omitted, as appearing to be the results of less exact observation; others, because there was no space for them in our figure. For instance, Mr. Penrose's determination coincides almost exactly with Professor Grant's.

Mr. Maclear, who observed the shower at the Royal Observatory, Cape of Good Hope, considers that the radiant point was nearer Regulus than, and about, but he did not particularly note its position. The meteors,

On one point the above evidence seems decisive. at the time of our encountering them, were neither crossing the earth's orbit from without inwards, nor from within outwards, by an appreciable angle. In the figure, the cross on the Ecliptic indicates the point on the celestial sphere towards which the earth was travelling at the moment of encounter-or, more exactly, the point towards which we in England were being carried by the combined effects of the earth's revolution and rotation. The dotted line indicates the longitude-circle through this point (which has been called the "apex of the earth's way "). Now, the fact that the radiant point lies in the neighbourhood of this point at all, shows that we meet the meteor-zone; the fact that the radiant-point lies about 10° to the north (along the dotted line) shows that the zone crosses the earth's orbit from the north southwards, at an angle greater than 10°, or, as it is technically expressed, that the meteors are at their descending node, when we encounter them. If the radiant-point had lain to the left of the dotted line, the fact would have shown that the zone crossed our orbit from within outwards-that is, that

*If we travel northwards against a rain-shower blown southwards, we are met more fully by the shower than if we are at rest; in other words, the shower seems to come from a point lower down towards the north: the amount of change depends on our velocity. Assuming the meteors' velocity not to differ greatly from the earth's (a probable assumption, as we shall see presently), the angle of 10° indicates a true inclination not differing greatly from 20°. Professor Newton's theory that the period of the meteors is 354 days, would make the angle about 19°.

the meteors were increasing their distance from the sun, while the reverse would have been shown if the radiant-point had been on the right. If we attach equal value to each of the determinations indicated in the figure, we must take as the mean position of the radiant a point not appreciably removed from the dotted line.

It follows that, either the orbit in which the meteoric zone or flight travels, is nearly circular, or (which seems less probable) that the descending node of the orbit coincides (very nearly) with its aphelion or perihelion distance. Assuming an orbit very nearly circular, we must assign to the meteors a period not differing by many days from that of our own earth. To account further for the period of thirty-three years, which separates successive recurrences of maximum intensity, we must have a period either exceeding or falling short of one year by about 1-33rd part, that is, by about eleven days. If we accept Ertel's view that the three cold days in May are due to the interposition of the meteor-zone between the earth and sun, we must suppose the mean distance of the meteors from the sun to be less than the earth's mean distance, and therefore we must take the shorter period, about 354 days. All the circumstances of the zone's motion may be determined with these data, and nothing is wanting but exact observations of the velocity with which the November meteors traverse our atmosphere, to establish Professor Newton's views on a sure basis. Professor Adams has gone through the requisite calculations for obtaining the approximate elements of the orbit; but confirmatory observations are as yet wanting.

Our readers are not to understand, however, that any doubt remains respecting the planetary motions of meteors. The mere mathematical evidence afforded by their apparent motions is sufficient to establish this point on as sure a basis as that of the Copernican theory itself. All that remains in doubt is the exact form and position of the orbit described by the meteor flight around the sun.

The observations made at the Cape Town Observatory are worthy of careful examination. Briefly, they amount to this:The display was well seen, but not quite so rich as in England; the time at which the shower reached its maximum was about 2h. 10m. A.M., Cape Mean Time, corresponding to about 1 A.M. Greenwich time; so that the display there reached its maximum about ten minutes or a quarter of an hour earlier (as to absolute time) than in England, where 1 h. 15 m. was noted as the hour of maximum intensity; at Cape Town, as in England, the period during which the display lasted (in a marked form) was about 2 hours. To interpret these results we must form a conception of the earth as it was actually situated during the night of November 14th. An observer placed

in space facing the earth, as it travelled onwards at the rate of 65,000 miles an hour would have seen its northern pole well within the darkened half-disc; England would have been brought into view before Cape Town,-England more than an hour before, Cape Town nearly an hour after, local midnight. Now, if between our observer and the advancing earth, there were situate a plane of meteors inclined 19° to the ecliptic, he would have seen the lower or southern half of the disc plunging first through the plane, the upper, or northern half, appearing last. The fact, then, that some ten minutes or a quarter of an hour elapsed between the maximum displays at Cape Town and England, is fully accounted for. The earth in that time travelled forwards some 14,000 miles, but its motion relatively to a plane inclined 19° to the ecliptic would be only one-third of this, or (roughly) about enough to shift the plane from Cape Town to England. The fact that the display was somewhat less rich at Cape Town is explained by the circumstance that the earth's surface encountered the plane less directly on the southern hemisphere, where contact first took place, than on the northern hemisphere, which was bowed down towards the plane. The fact that the display lasted nearly three hours shows that the thickness of the meteor zone cannot be less than 60,000 miles.

It

The fact that no display was seen in America does not prove, as many have supposed, that the extent of the zone is small. follows conclusively, from the results just examined, that America was on the following (or sheltered) hemisphere of the earth during the whole time that she occupied in plunging through the meteorzone. Therefore, the invisibility of the display in America affords additional evidence respecting the thickness of the zone, showing that it cannot greatly exceed the above-named estimate, but supplies no evidence whatever as to the extent of the zone.

From the fact that England was far advanced upon the earth's forward hemisphere at the epoch of maximum display, it is demonstrable that every meteor which then made its appearance above the horizon of any place in England, must have reached the earth's surface, or have been dissipated in the atmosphere,-unless we assume a height of several hundred miles for the meteors. Even this assumption, which is opposed to all evidence resulting from exact observation, would only allow the escape of a few meteors, seen low down towards the north-west. The fact that, for every meteor which grazes our atmosphere, hundreds must enter it in a direct line for the earth's surface, seems to have escaped the notice of many who have theorized on the subject. It shows that for all but the largest meteors our atmosphere acts as an efficient "buffer," deadening their impulse so thoroughly that they are vaporized by the heat equivalent to their lost velocity.

The spectrum-analysis of the November meteors appears to

have been less satisfactory than that of the August meteors effected by Mr. A. Herschel. The sudden cessation of the display prevented Mr. Herschel from attending to this point as he had intended to do. Mr. Browning notes the probable appearance of a yellow line in the spectra of several meteors, and of a line of green light in the spectra of two meteors.

Herr Schmidt's observation of the disappearance of the lunar crater Linné has received the attention it deserved. It seems to be now placed beyond a doubt that a change has occurred at this point of the moon's surface. Observers have often before had occasion to suspect the occurrence of variation, but hitherto there has been no observation so satisfactory as that made by Herr Schmidt. We not only have his evidence that he has been familiar with the mountain since 1841, but the drawings of Lohrmann (1823), who described the crater as very deep. It must be explained that, for the satisfactory observation of a lunar crater, the sun must have only a small elevation at that point of the moon's surface, in other words, we must observe the spot when near the terminator. The crater now obscured, used to become visible as a crater-that is, in shadow-when the sun's elevation was less than 5°. "Now," says Schmidt, "in lower altitudes of the sun, and close on the phase, not only is a crater never visible, but there appears, in a good light, and with magnifying powers of from 300 to 600 at most, a very delicate hill of 300 toises (about 1,920 English feet) in diameter, and 5 to 6 toises (about 35 feet) in height." As a light spot Linné continues always visible; as a crater it has entirely disappeared. From views taken lately by some of our most careful observers, it would seem as if the cloud, or haze, which appears to have hung over the crater, were being now gradually dissipated. Probably, in the course of a lunation or two, we shall have more definite intelligence. It will be well to avoid speculation until observation has done its work. In the meantime, we have additional evidence, if any were needed, of the value and necessity of the lunar-mapping now in progress.

We have again to refer to the variable T Coronæ, whose sudden outbreak formed one of the most noteworthy astronomical events of the year 1866. The whole significance of this occurrence depended on the question whether it were really a sudden outbreak, or whether the star arrived at its maximum of brilliancy by a gradual process of change. Mr. Hind, therefore, did well in calling the attention of astronomers to the reported observations of Mr. Barker, of Canada, who stated that he had seen the star on the 4th of May-eight days before the observation of Mr. Baxendell; and (subsequently) that he had noted a gradual increase of brilliancy up to May 12th. Herr Schmidt, on the other hand, expressed with confidence his opinion that the star was not con